threads / patch / 57118

patch, 2 partsgrep/pcre2: use PCRE2_UTF even with ASCII patterns

Subject: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns

## tl;dr

17 messages between Dec 18, 2021 and Feb 17, 2022. Diffs are folded; open one to read it.

replies: 16people: 4as markdown or json

René Scharfe· Dec 18, 2021, 19:50 UTC · lore

compile_pcre2_pattern() currently uses the option PCRE2_UTF only for patterns with non-ASCII characters. Patterns with ASCII wildcards can match non-ASCII strings, though. Without that option PCRE2 mishandles UTF-8 input, though -- it matches parts of multi-byte characters. Fix that by using PCRE2_UTF even for ASCII-only patterns.

This is a remake of the reverted ae39ba431a (grep/pcre2: fix an edge case concerning ascii patterns and UTF-8 data, 2021-10-15). The change to the condition and the test are simplified and more targeted.

Original-patch-by: Hamza Mahfooz <someguy@effective-light.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
---
 grep.c                          | 2 +-
 t/t7812-grep-icase-non-ascii.sh | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)
Show changes to 2 files +7 −2

grep.c, t/t7812-grep-icase-non-ascii.sh

diff --git a/grep.c b/grep.c
index fe847a0111..5badb6d851 100644
--- a/grep.c
+++ b/grep.c
@@ -382,7 +382,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 		}
 		options |= PCRE2_CASELESS;
 	}
-	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
+	if (!opt->ignore_locale && is_utf8_locale() &&
 	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
 		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);

diff --git a/t/t7812-grep-icase-non-ascii.sh b/t/t7812-grep-icase-non-ascii.sh
index e5d1e4ea68..ca3f24f807 100755
--- a/t/t7812-grep-icase-non-ascii.sh
+++ b/t/t7812-grep-icase-non-ascii.sh
@@ -123,4 +123,10 @@ test_expect_success GETTEXT_LOCALE,LIBPCRE2,PCRE2_MATCH_INVALID_UTF 'PCRE v2: gr
 	test_cmp invalid-0xe5 actual
 '

+test_expect_success GETTEXT_LOCALE,LIBPCRE2 'PCRE v2: grep non-literal ASCII from UTF-8' '
+	git grep --perl-regexp -h -o -e ll. file >actual &&
+	echo "lló" >expected &&
+	test_cmp expected actual
+'
+
 test_done
--
2.34.0
René Scharfe· Dec 18, 2021, 19:53 UTC · re: René Scharfe · lore

[PATCH 2/2] grep/pcre2: factor out literal variable

Patterns that contain no wildcards and don't have to be case-folded are literal. Give this condition a name to increase the readability of the boolean expression for enabling the option PCRE2_UTF.

Signed-off-by: René Scharfe <l.s.r@web.de>
---
 grep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
Show changes to grep.c +2 −3
diff --git a/grep.c b/grep.c
index 5badb6d851..2b6ac3205d 100644
--- a/grep.c
+++ b/grep.c
@@ -362,6 +362,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 	int jitret;
 	int patinforet;
 	size_t jitsizearg;
+	int literal = !opt->ignore_case && (p->fixed || p->is_fixed);

 	/*
 	 * Call pcre2_general_context_create() before calling any
@@ -382,8 +383,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 		}
 		options |= PCRE2_CASELESS;
 	}
-	if (!opt->ignore_locale && is_utf8_locale() &&
-	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
+	if (!opt->ignore_locale && is_utf8_locale() && !literal)
 		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);

 #ifdef GIT_PCRE2_VERSION_10_36_OR_HIGHER
--
2.34.0
Ævar Arnfjörð Bjarmason· Dec 19, 2021, 19:37 UTC · re: René Scharfe · lore

Re: [PATCH 2/2] grep/pcre2: factor out literal variable

On Sat, Dec 18 2021, René Scharfe wrote:
Show 31 quoted lines
> Patterns that contain no wildcards and don't have to be case-folded are
> literal.  Give this condition a name to increase the readability of the
> boolean expression for enabling the option PCRE2_UTF.
>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
>  grep.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/grep.c b/grep.c
> index 5badb6d851..2b6ac3205d 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -362,6 +362,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>  	int jitret;
>  	int patinforet;
>  	size_t jitsizearg;
> +	int literal = !opt->ignore_case && (p->fixed || p->is_fixed);
>
>  	/*
>  	 * Call pcre2_general_context_create() before calling any
> @@ -382,8 +383,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>  		}
>  		options |= PCRE2_CASELESS;
>  	}
> -	if (!opt->ignore_locale && is_utf8_locale() &&
> -	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
> +	if (!opt->ignore_locale && is_utf8_locale() && !literal)
>  		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);
>
>  #ifdef GIT_PCRE2_VERSION_10_36_OR_HIGHER

I think for this and 1/2 it would be really nice to pick up a version of Hamza's CI changes: https://lore.kernel.org/git/20211118084143.279174-2-someguy@effective-light.com/

Aside: Not needed for this change, but I wonder if we could benefit minutely
from:
    #ifdef PCRE2_LITERAL
    options |= PCRE2_LITERAL;
    #endif
It'll save PCRE2 the small effort of finding that we've got no metacharacters.
Junio C Hamano· Dec 20, 2021, 20:52 UTC · re: Ævar Arnfjörð Bjarmason · lore

Re: [PATCH 2/2] grep/pcre2: factor out literal variable

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
> I think for this and 1/2 it would be really nice to pick up a version of
> Hamza's CI changes:
> https://lore.kernel.org/git/20211118084143.279174-2-someguy@effective-light.com/

Are there so many incompatible versions of pcre2 library whose usage are subtly different that we need to protect ourselves with multiple variants in CI from breakages?

I doubt pcre2 library was _that_ bad.

Adding a special task that builds with the minimum version we support may not be too bad, but the library should be stable enough to allow us to declare it sufficient to test the most common version with the most common build options in our ordinary build job(s).

Ævar Arnfjörð Bjarmason· Dec 20, 2021, 22:03 UTC · re: Junio C Hamano · lore

Re: [PATCH 2/2] grep/pcre2: factor out literal variable

On Mon, Dec 20 2021, Junio C Hamano wrote:
Show 11 quoted lines
> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>> I think for this and 1/2 it would be really nice to pick up a version of
>> Hamza's CI changes:
>> https://lore.kernel.org/git/20211118084143.279174-2-someguy@effective-light.com/
>
> Are there so many incompatible versions of pcre2 library whose usage
> are subtly different that we need to protect ourselves with multiple
> variants in CI from breakages?
>
> I doubt pcre2 library was _that_ bad.
It's really not, but:
 * We have an optional >=10.34 feature we use (albeit trivial)
 * We have an optional >=10.36 feature we use (major, and directly related)
 * We might be targeting JIT or not, and the error handling isn't the same (known PCRE caveat)
 * We might be targeting a PCRE that knows about Unicode, or not
 * We use it in a mode where we might feed UTF-8 invalid data into the UTF-8 mode

Any update to the relevant code really needs to test the combination of those, so it's a perfect target for CI to make that less tedious.

> Adding a special task that builds with the minimum version we
> support may not be too bad, but the library should be stable enough
> to allow us to declare it sufficient to test the most common version
> with the most common build options in our ordinary build job(s).

That's a nice idea, but not the reality of the situation. Unless we're willing to bump the version requirement & insist on JIT && Unicode support before using it.

The CI itself should be realtively cheap, and just runs the few tests that would spot any breakages with the above.

Junio C Hamano· Dec 20, 2021, 20:53 UTC · re: Ævar Arnfjörð Bjarmason · lore

Re: [PATCH 2/2] grep/pcre2: factor out literal variable

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
Show 8 quoted lines
> Aside: Not needed for this change, but I wonder if we could benefit minutely
> from:
>
>     #ifdef PCRE2_LITERAL
>     options |= PCRE2_LITERAL;
>     #endif
>
> It'll save PCRE2 the small effort of finding that we've got no metacharacters.

After the dust settles, it would be a good addition in a separate patch.

Thanks.
Junio C Hamano· Dec 20, 2021, 20:47 UTC · re: René Scharfe · lore

Re: [PATCH 2/2] grep/pcre2: factor out literal variable

René Scharfe <l.s.r@web.de> writes:
> Patterns that contain no wildcards and don't have to be case-folded are
> literal.  Give this condition a name to increase the readability of the
> boolean expression for enabling the option PCRE2_UTF.
Makes sense.  Quite a lot.
Thanks.
SZEDER Gábor· Jan 29, 2022, 17:25 UTC · re: René Scharfe · lore

[v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

On Sat, Dec 18, 2021 at 08:50:02PM +0100, René Scharfe wrote:
Show 30 quoted lines
> compile_pcre2_pattern() currently uses the option PCRE2_UTF only for
> patterns with non-ASCII characters.  Patterns with ASCII wildcards can
> match non-ASCII strings, though.  Without that option PCRE2 mishandles
> UTF-8 input, though -- it matches parts of multi-byte characters.  Fix
> that by using PCRE2_UTF even for ASCII-only patterns.
> 
> This is a remake of the reverted ae39ba431a (grep/pcre2: fix an edge
> case concerning ascii patterns and UTF-8 data, 2021-10-15).  The change
> to the condition and the test are simplified and more targeted.
> 
> Original-patch-by: Hamza Mahfooz <someguy@effective-light.com>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
>  grep.c                          | 2 +-
>  t/t7812-grep-icase-non-ascii.sh | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/grep.c b/grep.c
> index fe847a0111..5badb6d851 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -382,7 +382,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>  		}
>  		options |= PCRE2_CASELESS;
>  	}
> -	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
> +	if (!opt->ignore_locale && is_utf8_locale() &&
>  	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
>  		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);
>

I tried to use 'git grep -P' for the first time ever, and it hung right away, spinning all CPUs at 100%. I could narrow it down, both the complexity of the pattern and the size of the input, see the test below, and it bisects to this patch.

  ---   >8   ---
#!/bin/sh
test_description='test'
. ./test-lib.sh
test_expect_success PCRE 'test' '
	# LC_ALL=C works
	LC_ALL=en_US.UTF-8 &&
	cat >ascii <<-\EOF &&
	foo
	 bar
	 baz
	EOF
	cat >utf8 <<-\EOF &&
	foo
	 bar
	 báz
	EOF
	git add ascii utf8 &&
	# These all work as expected:
	git grep --threads=1 -P " " ascii &&
	git grep --threads=1 -P "^ " ascii &&
	git grep --threads=1 -P "\s" ascii &&
	git grep --threads=1 -P "^\s" ascii &&
	git grep --threads=1 -P " " utf8 &&
	git grep --threads=1 -P "^ " utf8 &&
	git grep --threads=1 -P "\s" utf8 &&
	# This hangs (but it does work with basic and extended regexp):
	git grep --threads=1 -P "^\s" utf8
'
test_done
René Scharfe· Jan 30, 2022, 07:55 UTC · re: SZEDER Gábor · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

Am 29.01.22 um 18:25 schrieb SZEDER Gábor:
Show 75 quoted lines
> On Sat, Dec 18, 2021 at 08:50:02PM +0100, René Scharfe wrote:
>> compile_pcre2_pattern() currently uses the option PCRE2_UTF only for
>> patterns with non-ASCII characters.  Patterns with ASCII wildcards can
>> match non-ASCII strings, though.  Without that option PCRE2 mishandles
>> UTF-8 input, though -- it matches parts of multi-byte characters.  Fix
>> that by using PCRE2_UTF even for ASCII-only patterns.
>>
>> This is a remake of the reverted ae39ba431a (grep/pcre2: fix an edge
>> case concerning ascii patterns and UTF-8 data, 2021-10-15).  The change
>> to the condition and the test are simplified and more targeted.
>>
>> Original-patch-by: Hamza Mahfooz <someguy@effective-light.com>
>> Signed-off-by: René Scharfe <l.s.r@web.de>
>> ---
>>  grep.c                          | 2 +-
>>  t/t7812-grep-icase-non-ascii.sh | 6 ++++++
>>  2 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/grep.c b/grep.c
>> index fe847a0111..5badb6d851 100644
>> --- a/grep.c
>> +++ b/grep.c
>> @@ -382,7 +382,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>>  		}
>>  		options |= PCRE2_CASELESS;
>>  	}
>> -	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
>> +	if (!opt->ignore_locale && is_utf8_locale() &&
>>  	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
>>  		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);
>>
>
> I tried to use 'git grep -P' for the first time ever, and it hung
> right away, spinning all CPUs at 100%.  I could narrow it down, both
> the complexity of the pattern and the size of the input, see the test
> below, and it bisects to this patch.
>
>
>   ---   >8   ---
>
> #!/bin/sh
>
> test_description='test'
>
> . ./test-lib.sh
>
> test_expect_success PCRE 'test' '
> 	# LC_ALL=C works
> 	LC_ALL=en_US.UTF-8 &&
> 	cat >ascii <<-\EOF &&
> 	foo
> 	 bar
> 	 baz
> 	EOF
> 	cat >utf8 <<-\EOF &&
> 	foo
> 	 bar
> 	 báz
> 	EOF
> 	git add ascii utf8 &&
>
> 	# These all work as expected:
> 	git grep --threads=1 -P " " ascii &&
> 	git grep --threads=1 -P "^ " ascii &&
> 	git grep --threads=1 -P "\s" ascii &&
> 	git grep --threads=1 -P "^\s" ascii &&
> 	git grep --threads=1 -P " " utf8 &&
> 	git grep --threads=1 -P "^ " utf8 &&
> 	git grep --threads=1 -P "\s" utf8 &&
>
> 	# This hangs (but it does work with basic and extended regexp):
> 	git grep --threads=1 -P "^\s" utf8
> '
>
> test_done
I get the following result and no hang with PCRE2 10.39:
   utf8: bar
   utf8: báz

e0c6029 (Fix inifinite loop when a single byte newline is searched in JIT., 2020-05-29) [1] sounds like it might have fixed it. It's part of version 10.36.

Do you still get the error when you disable JIT, i.e. when you use the pattern "(*NO_JIT)^\s" instead?

René
[1] https://github.com/PhilipHazel/pcre2/commit/e0c6029a62db9c2161941ecdf459205382d4d379
SZEDER Gábor· Jan 30, 2022, 09:04 UTC · re: René Scharfe · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

On Sun, Jan 30, 2022 at 08:55:02AM +0100, René Scharfe wrote:
Show 85 quoted lines
> Am 29.01.22 um 18:25 schrieb SZEDER Gábor:
> > On Sat, Dec 18, 2021 at 08:50:02PM +0100, René Scharfe wrote:
> >> compile_pcre2_pattern() currently uses the option PCRE2_UTF only for
> >> patterns with non-ASCII characters.  Patterns with ASCII wildcards can
> >> match non-ASCII strings, though.  Without that option PCRE2 mishandles
> >> UTF-8 input, though -- it matches parts of multi-byte characters.  Fix
> >> that by using PCRE2_UTF even for ASCII-only patterns.
> >>
> >> This is a remake of the reverted ae39ba431a (grep/pcre2: fix an edge
> >> case concerning ascii patterns and UTF-8 data, 2021-10-15).  The change
> >> to the condition and the test are simplified and more targeted.
> >>
> >> Original-patch-by: Hamza Mahfooz <someguy@effective-light.com>
> >> Signed-off-by: René Scharfe <l.s.r@web.de>
> >> ---
> >>  grep.c                          | 2 +-
> >>  t/t7812-grep-icase-non-ascii.sh | 6 ++++++
> >>  2 files changed, 7 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/grep.c b/grep.c
> >> index fe847a0111..5badb6d851 100644
> >> --- a/grep.c
> >> +++ b/grep.c
> >> @@ -382,7 +382,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
> >>  		}
> >>  		options |= PCRE2_CASELESS;
> >>  	}
> >> -	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
> >> +	if (!opt->ignore_locale && is_utf8_locale() &&
> >>  	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
> >>  		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);
> >>
> >
> > I tried to use 'git grep -P' for the first time ever, and it hung
> > right away, spinning all CPUs at 100%.  I could narrow it down, both
> > the complexity of the pattern and the size of the input, see the test
> > below, and it bisects to this patch.
> >
> >
> >   ---   >8   ---
> >
> > #!/bin/sh
> >
> > test_description='test'
> >
> > . ./test-lib.sh
> >
> > test_expect_success PCRE 'test' '
> > 	# LC_ALL=C works
> > 	LC_ALL=en_US.UTF-8 &&
> > 	cat >ascii <<-\EOF &&
> > 	foo
> > 	 bar
> > 	 baz
> > 	EOF
> > 	cat >utf8 <<-\EOF &&
> > 	foo
> > 	 bar
> > 	 báz
> > 	EOF
> > 	git add ascii utf8 &&
> >
> > 	# These all work as expected:
> > 	git grep --threads=1 -P " " ascii &&
> > 	git grep --threads=1 -P "^ " ascii &&
> > 	git grep --threads=1 -P "\s" ascii &&
> > 	git grep --threads=1 -P "^\s" ascii &&
> > 	git grep --threads=1 -P " " utf8 &&
> > 	git grep --threads=1 -P "^ " utf8 &&
> > 	git grep --threads=1 -P "\s" utf8 &&
> >
> > 	# This hangs (but it does work with basic and extended regexp):
> > 	git grep --threads=1 -P "^\s" utf8
> > '
> >
> > test_done
> 
> I get the following result and no hang with PCRE2 10.39:
> 
>    utf8: bar
>    utf8: báz
> 
> e0c6029 (Fix inifinite loop when a single byte newline is searched in
> JIT., 2020-05-29) [1] sounds like it might have fixed it.  It's part of
> version 10.36.

I saw this hang on two Ubuntu 20.04 based boxes, which predate that fix you mention only by a month or two, and apparently the almost two years since then was not enough for this fix to trickle down into updated 20.04 pcre packages, because:

> Do you still get the error when you disable JIT, i.e. when you use the
> pattern "(*NO_JIT)^\s" instead?
No, with this pattern it works as expected.

So is there a more convenient way to disable PCRE JIT in Git? FWIW, (non-git) 'grep -P' works with the same patterns.

> René
> 
> 
> [1] https://github.com/PhilipHazel/pcre2/commit/e0c6029a62db9c2161941ecdf459205382d4d379
René Scharfe· Jan 30, 2022, 13:32 UTC · re: SZEDER Gábor · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

Am 30.01.22 um 10:04 schrieb SZEDER Gábor:
Show 17 quoted lines
> On Sun, Jan 30, 2022 at 08:55:02AM +0100, René Scharfe wrote:
>> e0c6029 (Fix inifinite loop when a single byte newline is searched in
>> JIT., 2020-05-29) [1] sounds like it might have fixed it.  It's part of
>> version 10.36.
>
> I saw this hang on two Ubuntu 20.04 based boxes, which predate that
> fix you mention only by a month or two, and apparently the almost two
> years since then was not enough for this fix to trickle down into
> updated 20.04 pcre packages, because:
>
>> Do you still get the error when you disable JIT, i.e. when you use the
>> pattern "(*NO_JIT)^\s" instead?
>
> No, with this pattern it works as expected.
>
> So is there a more convenient way to disable PCRE JIT in Git?  FWIW,
> (non-git) 'grep -P' works with the same patterns.
I don't know a better way.  We could do it automatically, though:
--- >8 ---
Subject: [PATCH] grep: disable JIT on PCRE2 before 10.36 to avoid endless loop

Commit e0c6029 (Fix inifinite loop when a single byte newline is searched in JIT., 2020-05-29) of PCRE2 adds the following point to its ChangeLog for version 10.36:

  2. Fix inifinite loop when a single byte newline is searched in JIT when
  invalid utf8 mode is enabled.

Avoid that bug on older versions (which are still reportedly found in the wild) by disabling the JIT when handling UTF-8.

Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
---
Not sure how to test it.  Killing git grep after a second or so seems a
bit clumsy.  timeout(1) from GNU coreutils at least allows doing that
from the shell, but it's not a standard tool.  Perhaps we need a new
test helper for that purpose?
 grep.c | 8 ++++++++
 1 file changed, 8 insertions(+)
Show changes to grep.c +8 −1
diff --git a/grep.c b/grep.c
index 7bb0360869..16629a2301 100644
--- a/grep.c
+++ b/grep.c
@@ -406,6 +406,14 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 	}

 	pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
+#ifndef GIT_PCRE2_VERSION_10_36_OR_HIGHER
+	/*
+	 * Work around the bug fixed by e0c6029 (Fix inifinite loop when a
+	 * single byte newline is searched in JIT., 2020-05-29).
+	 */
+	if (options & PCRE2_MATCH_INVALID_UTF)
+		p->pcre2_jit_on = 0;
+#endif
 	if (p->pcre2_jit_on) {
 		jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
 		if (jitret)
--
2.35.0
Ævar Arnfjörð Bjarmason· Jan 31, 2022, 21:01 UTC · re: René Scharfe · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

On Sun, Jan 30 2022, René Scharfe wrote:
Show 56 quoted lines
> Am 30.01.22 um 10:04 schrieb SZEDER Gábor:
>> On Sun, Jan 30, 2022 at 08:55:02AM +0100, René Scharfe wrote:
>>> e0c6029 (Fix inifinite loop when a single byte newline is searched in
>>> JIT., 2020-05-29) [1] sounds like it might have fixed it.  It's part of
>>> version 10.36.
>>
>> I saw this hang on two Ubuntu 20.04 based boxes, which predate that
>> fix you mention only by a month or two, and apparently the almost two
>> years since then was not enough for this fix to trickle down into
>> updated 20.04 pcre packages, because:
>>
>>> Do you still get the error when you disable JIT, i.e. when you use the
>>> pattern "(*NO_JIT)^\s" instead?
>>
>> No, with this pattern it works as expected.
>>
>> So is there a more convenient way to disable PCRE JIT in Git?  FWIW,
>> (non-git) 'grep -P' works with the same patterns.
>
> I don't know a better way.  We could do it automatically, though:
>
> --- >8 ---
> Subject: [PATCH] grep: disable JIT on PCRE2 before 10.36 to avoid endless loop
>
> Commit e0c6029 (Fix inifinite loop when a single byte newline is
> searched in JIT., 2020-05-29) of PCRE2 adds the following point to its
> ChangeLog for version 10.36:
>
>   2. Fix inifinite loop when a single byte newline is searched in JIT when
>   invalid utf8 mode is enabled.
>
> Avoid that bug on older versions (which are still reportedly found in
> the wild) by disabling the JIT when handling UTF-8.
>
> Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
> Not sure how to test it.  Killing git grep after a second or so seems a
> bit clumsy.  timeout(1) from GNU coreutils at least allows doing that
> from the shell, but it's not a standard tool.  Perhaps we need a new
> test helper for that purpose?
>
>  grep.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/grep.c b/grep.c
> index 7bb0360869..16629a2301 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -406,6 +406,14 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>  	}
>
>  	pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
> +#ifndef GIT_PCRE2_VERSION_10_36_OR_HIGHER
> +	/*
> +	 * Work around the bug fixed by e0c6029 (Fix inifinite loop when a

Better to quote this as PhilipHazel/pcre2@e0c6029 or something, i.e. to indicate that it's not git.git's commit.

> +	 * single byte newline is searched in JIT., 2020-05-29).
> +	 */
> +	if (options & PCRE2_MATCH_INVALID_UTF)
> +		p->pcre2_jit_on = 0;

It seems rather heavy-hande, but I can't think of a better way to deal with this, i.e. if we selectively use JIT on older versions, surely we run into the match-bytes-but-want-chars bug you were fixing.

> +#endif
>  	if (p->pcre2_jit_on) {
>  		jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
>  		if (jitret)
René Scharfe· Feb 5, 2022, 17:00 UTC · re: Ævar Arnfjörð Bjarmason · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

Am 31.01.22 um 22:01 schrieb Ævar Arnfjörð Bjarmason:
Show 44 quoted lines
>
> On Sun, Jan 30 2022, René Scharfe wrote:
>
>> Am 30.01.22 um 10:04 schrieb SZEDER Gábor:
>>> On Sun, Jan 30, 2022 at 08:55:02AM +0100, René Scharfe wrote:
>>>> e0c6029 (Fix inifinite loop when a single byte newline is searched in
>>>> JIT., 2020-05-29) [1] sounds like it might have fixed it.  It's part of
>>>> version 10.36.
>>>
>>> I saw this hang on two Ubuntu 20.04 based boxes, which predate that
>>> fix you mention only by a month or two, and apparently the almost two
>>> years since then was not enough for this fix to trickle down into
>>> updated 20.04 pcre packages, because:
>>>
>>>> Do you still get the error when you disable JIT, i.e. when you use the
>>>> pattern "(*NO_JIT)^\s" instead?
>>>
>>> No, with this pattern it works as expected.
>>>
>>> So is there a more convenient way to disable PCRE JIT in Git?  FWIW,
>>> (non-git) 'grep -P' works with the same patterns.
>>
>> I don't know a better way.  We could do it automatically, though:
>>
>> --- >8 ---
>> Subject: [PATCH] grep: disable JIT on PCRE2 before 10.36 to avoid endless loop
>>
>> Commit e0c6029 (Fix inifinite loop when a single byte newline is
>> searched in JIT., 2020-05-29) of PCRE2 adds the following point to its
>> ChangeLog for version 10.36:
>>
>>   2. Fix inifinite loop when a single byte newline is searched in JIT when
>>   invalid utf8 mode is enabled.
>>
>> Avoid that bug on older versions (which are still reportedly found in
>> the wild) by disabling the JIT when handling UTF-8.
>>
>> Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
>> Signed-off-by: René Scharfe <l.s.r@web.de>
>> ---
>> Not sure how to test it.  Killing git grep after a second or so seems a
>> bit clumsy.  timeout(1) from GNU coreutils at least allows doing that
>> from the shell, but it's not a standard tool.  Perhaps we need a new
>> test helper for that purpose?

https://mywiki.wooledge.org/BashFAQ/068 offers a Perl-based Shell function or aborting a program if it takes too long:

   doalarm() { perl -e 'alarm shift; exec @ARGV' -- "$@"; }

It doesn't waste time when the program finishes faster and seems to work fine with git grep.

I can't actually test the effectiveness of the patch because PCRE2's JIT doesn't work on my development machine at all (Apple M1), as I just discovered. :-/ While we know that disabling JIT helps, we didn't actually determine, yet, if e0c6029 (Fix inifinite loop when a single byte newline is searched in JIT., 2020-05-29) really fixes the "^\s" bug.

So I have to abandon this patch, unfortunately. Any volunteer to pick it up?

Show 18 quoted lines
>>
>>  grep.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/grep.c b/grep.c
>> index 7bb0360869..16629a2301 100644
>> --- a/grep.c
>> +++ b/grep.c
>> @@ -406,6 +406,14 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>>  	}
>>
>>  	pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
>> +#ifndef GIT_PCRE2_VERSION_10_36_OR_HIGHER
>> +	/*
>> +	 * Work around the bug fixed by e0c6029 (Fix inifinite loop when a
>
> Better to quote this as PhilipHazel/pcre2@e0c6029 or something, i.e. to
> indicate that it's not git.git's commit.

The context should suffice for a human reader to understand that it's a PCRE2 about a bug fix, but I can see some program turning hex strings into repo-local links getting confused. Is there a standard cross-repo citation format? Using a Github link might be the most practical way for the near term, I suspect.

Show 15 quoted lines
>
>> +	 * single byte newline is searched in JIT., 2020-05-29).
>> +	 */
>> +	if (options & PCRE2_MATCH_INVALID_UTF)
>> +		p->pcre2_jit_on = 0;
>
> It seems rather heavy-hande, but I can't think of a better way to deal
> with this, i.e. if we selectively use JIT on older versions, surely we
> run into the match-bytes-but-want-chars bug you were fixing.
>
>> +#endif
>>  	if (p->pcre2_jit_on) {
>>  		jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
>>  		if (jitret)
>
SZEDER Gábor· Feb 6, 2022, 10:08 UTC · re: René Scharfe · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

On Sat, Feb 05, 2022 at 06:00:02PM +0100, René Scharfe wrote:
Show 38 quoted lines
> >> --- >8 ---
> >> Subject: [PATCH] grep: disable JIT on PCRE2 before 10.36 to avoid endless loop
> >>
> >> Commit e0c6029 (Fix inifinite loop when a single byte newline is
> >> searched in JIT., 2020-05-29) of PCRE2 adds the following point to its
> >> ChangeLog for version 10.36:
> >>
> >>   2. Fix inifinite loop when a single byte newline is searched in JIT when
> >>   invalid utf8 mode is enabled.
> >>
> >> Avoid that bug on older versions (which are still reportedly found in
> >> the wild) by disabling the JIT when handling UTF-8.
> >>
> >> Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
> >> Signed-off-by: René Scharfe <l.s.r@web.de>
> >> ---
> >> Not sure how to test it.  Killing git grep after a second or so seems a
> >> bit clumsy.  timeout(1) from GNU coreutils at least allows doing that
> >> from the shell, but it's not a standard tool.  Perhaps we need a new
> >> test helper for that purpose?
> 
> https://mywiki.wooledge.org/BashFAQ/068 offers a Perl-based Shell
> function or aborting a program if it takes too long:
> 
>    doalarm() { perl -e 'alarm shift; exec @ARGV' -- "$@"; }
> 
> It doesn't waste time when the program finishes faster and seems to work
> fine with git grep.
> 
> I can't actually test the effectiveness of the patch because PCRE2's
> JIT doesn't work on my development machine at all (Apple M1), as I just
> discovered. :-/  While we know that disabling JIT helps, we didn't
> actually determine, yet, if e0c6029 (Fix inifinite loop when a single
> byte newline is searched in JIT., 2020-05-29) really fixes the "^\s"
> bug.
> 
> So I have to abandon this patch, unfortunately.  Any volunteer to pick
> it up?

FWIW, I built Git with your patch and USE_LIBPCRE2=YesPlease and run the test suite, and it succeeded. Though I can't judge how much is this actually worth.

Ævar Arnfjörð Bjarmason· Feb 12, 2022, 20:46 UTC · re: René Scharfe · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

On Sat, Feb 05 2022, René Scharfe wrote:
Show 63 quoted lines
> Am 31.01.22 um 22:01 schrieb Ævar Arnfjörð Bjarmason:
>>
>> On Sun, Jan 30 2022, René Scharfe wrote:
>>
>>> Am 30.01.22 um 10:04 schrieb SZEDER Gábor:
>>>> On Sun, Jan 30, 2022 at 08:55:02AM +0100, René Scharfe wrote:
>>>>> e0c6029 (Fix inifinite loop when a single byte newline is searched in
>>>>> JIT., 2020-05-29) [1] sounds like it might have fixed it.  It's part of
>>>>> version 10.36.
>>>>
>>>> I saw this hang on two Ubuntu 20.04 based boxes, which predate that
>>>> fix you mention only by a month or two, and apparently the almost two
>>>> years since then was not enough for this fix to trickle down into
>>>> updated 20.04 pcre packages, because:
>>>>
>>>>> Do you still get the error when you disable JIT, i.e. when you use the
>>>>> pattern "(*NO_JIT)^\s" instead?
>>>>
>>>> No, with this pattern it works as expected.
>>>>
>>>> So is there a more convenient way to disable PCRE JIT in Git?  FWIW,
>>>> (non-git) 'grep -P' works with the same patterns.
>>>
>>> I don't know a better way.  We could do it automatically, though:
>>>
>>> --- >8 ---
>>> Subject: [PATCH] grep: disable JIT on PCRE2 before 10.36 to avoid endless loop
>>>
>>> Commit e0c6029 (Fix inifinite loop when a single byte newline is
>>> searched in JIT., 2020-05-29) of PCRE2 adds the following point to its
>>> ChangeLog for version 10.36:
>>>
>>>   2. Fix inifinite loop when a single byte newline is searched in JIT when
>>>   invalid utf8 mode is enabled.
>>>
>>> Avoid that bug on older versions (which are still reportedly found in
>>> the wild) by disabling the JIT when handling UTF-8.
>>>
>>> Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
>>> Signed-off-by: René Scharfe <l.s.r@web.de>
>>> ---
>>> Not sure how to test it.  Killing git grep after a second or so seems a
>>> bit clumsy.  timeout(1) from GNU coreutils at least allows doing that
>>> from the shell, but it's not a standard tool.  Perhaps we need a new
>>> test helper for that purpose?
>
> https://mywiki.wooledge.org/BashFAQ/068 offers a Perl-based Shell
> function or aborting a program if it takes too long:
>
>    doalarm() { perl -e 'alarm shift; exec @ARGV' -- "$@"; }
>
> It doesn't waste time when the program finishes faster and seems to work
> fine with git grep.
>
> I can't actually test the effectiveness of the patch because PCRE2's
> JIT doesn't work on my development machine at all (Apple M1), as I just
> discovered. :-/  While we know that disabling JIT helps, we didn't
> actually determine, yet, if e0c6029 (Fix inifinite loop when a single
> byte newline is searched in JIT., 2020-05-29) really fixes the "^\s"
> bug.
>
> So I have to abandon this patch, unfortunately.  Any volunteer to pick
> it up?

We can test it in CI, and have a proposed patch from Hamza Mahfooz to do so. See https://lore.kernel.org/git/211220.865yrjszg4.gmgdl@evledraar.gmail.com/

There's been some minor changes to the main.yml since then, but I think you should be able to just pick that patch up, adjust it, apply whatever changes you want to test on top, and push it to github.

René Scharfe· Feb 17, 2022, 21:14 UTC · re: Ævar Arnfjörð Bjarmason · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

Am 12.02.22 um 21:46 schrieb Ævar Arnfjörð Bjarmason:
Show 21 quoted lines
>
> On Sat, Feb 05 2022, René Scharfe wrote:
>
>>
>> I can't actually test the effectiveness of the patch because PCRE2's
>> JIT doesn't work on my development machine at all (Apple M1), as I just
>> discovered. :-/  While we know that disabling JIT helps, we didn't
>> actually determine, yet, if e0c6029 (Fix inifinite loop when a single
>> byte newline is searched in JIT., 2020-05-29) really fixes the "^\s"
>> bug.
>>
>> So I have to abandon this patch, unfortunately.  Any volunteer to pick
>> it up?
>
> We can test it in CI, and have a proposed patch from Hamza Mahfooz to do
> so. See
> https://lore.kernel.org/git/211220.865yrjszg4.gmgdl@evledraar.gmail.com/
>
> There's been some minor changes to the main.yml since then, but I think
> you should be able to just pick that patch up, adjust it, apply whatever
> changes you want to test on top, and push it to github.
Good idea!  Except the "just" is not justified, I feel.  I learned that
  - t7810 fails with PCRE2 built with --disable-unicode because it uses
    \p{...} unconditionally, and that's not supported without Unicode
    support -- no idea how to detect that and skip those tests except
    by trying and maybe looking for the note that "this version of PCRE2
    does not have support for \P, \p, or \X", which somehow feels iffy,
  - PCRE2 10.35 doesn't build on Ubuntu x64 without adding -mshstk to
    CFLAGS, and that's the version I wanted to test,
  - many of the Unicode related tests require Islandic language support,
    and "sudo apt-get -y install `check-language-support -l is`"
    installs it,
  - the condition for our workaround for bug 2642 is reversed,
  - with that fixed I can't trigger the endless loop.

So perhaps that's the only fix we need here -- or perhaps I got confused by the multitude of options.

--- >8 ---
Subject: [PATCH] grep: fix triggering PCRE2_NO_START_OPTIMIZE workaround

PCRE2 bug 2642 was fixed in version 10.36. Our 95ca1f987e (grep/pcre2: better support invalid UTF-8 haystacks, 2021-01-24) worked around it on older versions by setting the flag PCRE2_NO_START_OPTIMIZE. 797c359978 (grep/pcre2: use compile-time PCREv2 version test, 2021-02-18) switched it around to set the flag on 10.36 and higher instead, while it claimed to use "the same test done at compile-time".

Switch the condition back to apply the workaround on PCRE2 versions _before_ 10.36.

Signed-off-by: René Scharfe <l.s.r@web.de>
---
 grep.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Show changes to grep.c +1 −2
diff --git a/grep.c b/grep.c
index 5bec7fd793..ef34d764f9 100644
--- a/grep.c
+++ b/grep.c
@@ -386,7 +386,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 	if (!opt->ignore_locale && is_utf8_locale() && !literal)
 		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);

-#ifdef GIT_PCRE2_VERSION_10_36_OR_HIGHER
+#ifndef GIT_PCRE2_VERSION_10_36_OR_HIGHER
 	/* Work around https://bugs.exim.org/show_bug.cgi?id=2642 fixed in 10.36 */
 	if (PCRE2_MATCH_INVALID_UTF && options & (PCRE2_UTF | PCRE2_CASELESS))
 		options |= PCRE2_NO_START_OPTIMIZE;
--
2.35.1
Junio C Hamano· Feb 17, 2022, 22:56 UTC · re: René Scharfe · lore

Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale

René Scharfe <l.s.r@web.de> writes:
Show 28 quoted lines
> Subject: [PATCH] grep: fix triggering PCRE2_NO_START_OPTIMIZE workaround
>
> PCRE2 bug 2642 was fixed in version 10.36.  Our 95ca1f987e (grep/pcre2:
> better support invalid UTF-8 haystacks, 2021-01-24) worked around it on
> older versions by setting the flag PCRE2_NO_START_OPTIMIZE.  797c359978
> (grep/pcre2: use compile-time PCREv2 version test, 2021-02-18) switched
> it around to set the flag on 10.36 and higher instead, while it claimed
> to use "the same test done at compile-time".
>
> Switch the condition back to apply the workaround on PCRE2 versions
> _before_ 10.36.
>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
>  grep.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/grep.c b/grep.c
> index 5bec7fd793..ef34d764f9 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -386,7 +386,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>  	if (!opt->ignore_locale && is_utf8_locale() && !literal)
>  		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);
>
> -#ifdef GIT_PCRE2_VERSION_10_36_OR_HIGHER
> +#ifndef GIT_PCRE2_VERSION_10_36_OR_HIGHER
>  	/* Work around https://bugs.exim.org/show_bug.cgi?id=2642 fixed in 10.36 */

Oh, that's embarrassing. The #ifdef and the comment sit next to each other and they make contradicting statement.

>  	if (PCRE2_MATCH_INVALID_UTF && options & (PCRE2_UTF | PCRE2_CASELESS))
>  		options |= PCRE2_NO_START_OPTIMIZE;
> --
> 2.35.1

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