threads / patch / 33100

patchsetup.c: Fix prefix_pathspec from looping pass end of string

Subject: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

## tl;dr

9 messages between Mar 7, 2013 and Mar 9, 2013. Diffs are folded; open one to read it.

replies: 8people: 2as markdown or json

Andrew Wong· Mar 7, 2013, 16:36 UTC · lore

The previous code was assuming length ends at either `)` or `,`, and was not handling the case where strcspn returns length due to end of string. So specifying ":(top" as pathspec will cause the loop to go pass the end of string.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 setup.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Show changes to setup.c +4 −2

diff --git a/setup.c b/setup.c
index 1dee47e..f4c4e73 100644
--- a/setup.c
+++ b/setup.c
@@ -207,9 +207,11 @@ static const char *prefix_pathspec(const char *prefix, int prefixlen, const char
 		     *copyfrom && *copyfrom != ')';
 		     copyfrom = nextat) {
 			size_t len = strcspn(copyfrom, ",)");
-			if (copyfrom[len] == ')')
+			if (copyfrom[len] == '\0')
 				nextat = copyfrom + len;
-			else
+			else if (copyfrom[len] == ')')
+				nextat = copyfrom + len;
+			else if (copyfrom[len] == ',')
 				nextat = copyfrom + len + 1;
 			if (!len)
 				continue;

-- 
1.8.2.rc0.22.gb3600c3

Junio C Hamano· Mar 7, 2013, 21:48 UTC · re: Andrew Wong · lore

Re: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

Andrew Wong <andrew.kw.w@gmail.com> writes:

> The previous code was assuming length ends at either `)` or `,`, and was
> not handling the case where strcspn returns length due to end of string.
> So specifying ":(top" as pathspec will cause the loop to go pass the end
> of string.

Thanks.

The parser that goes past the end of the string may be a bug worth fixing, but is this patch sufficient to diagnose such an input as an error?

Show 23 quoted lines

> Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
> ---
>  setup.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/setup.c b/setup.c
> index 1dee47e..f4c4e73 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -207,9 +207,11 @@ static const char *prefix_pathspec(const char *prefix, int prefixlen, const char
>  		     *copyfrom && *copyfrom != ')';
>  		     copyfrom = nextat) {
>  			size_t len = strcspn(copyfrom, ",)");
> -			if (copyfrom[len] == ')')
> +			if (copyfrom[len] == '\0')
>  				nextat = copyfrom + len;
> -			else
> +			else if (copyfrom[len] == ')')
> +				nextat = copyfrom + len;
> +			else if (copyfrom[len] == ',')
>  				nextat = copyfrom + len + 1;
>  			if (!len)
>  				continue;

Andrew Wong· Mar 7, 2013, 22:25 UTC · re: Junio C Hamano · lore

Re: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

On 3/7/13, Junio C Hamano <gitster@pobox.com> wrote:

> The parser that goes past the end of the string may be a bug worth
> fixing, but is this patch sufficient to diagnose such an input as an
> error?

Yea, the patch should fix the passing end of string too. The parser was going past end of string because the nextat is set to "copyfrom + len + 1" for the '\0' case too. Then "+ 1" causes the parser to go pass end of string. If we handle the '\0' case separately, then the parser ends properly, and shouldn't be able to go pass the end of string.

Hm, should I be paranoid and put an "else" clause to call die() as well? In case there's a scenario where none of the 3 cases is true...

Andrew

Junio C Hamano· Mar 7, 2013, 23:59 UTC · re: Andrew Wong · lore

Re: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

Andrew Wong <andrew.kw.w@gmail.com> writes:

Show 11 quoted lines

> On 3/7/13, Junio C Hamano <gitster@pobox.com> wrote:
>> The parser that goes past the end of the string may be a bug worth
>> fixing, but is this patch sufficient to diagnose such an input as an
>> error?
>
> Yea, the patch should fix the passing end of string too. The parser
> was going past end of string because the nextat is set to "copyfrom +
> len + 1" for the '\0' case too. Then "+ 1" causes the parser to go
> pass end of string. If we handle the '\0' case separately, then the
> parser ends properly, and shouldn't be able to go pass the end of
> string.

This did not error out for me, though.

    $ cd t && git ls-files ":(top"

Andrew Wong· Mar 8, 2013, 00:25 UTC · re: Junio C Hamano · lore

Re: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

On 3/7/13, Junio C Hamano <gitster@pobox.com> wrote:

> This did not error out for me, though.
>
>     $ cd t && git ls-files ":(top"

No error message at all? Hm, maybe in your case, the byte after the end of string happens to be '\0' and the loop ended by chance?

git doesn't crash for me, but it generates this error:
    $ git ls-files ":(top"
    fatal: Invalid pathspec magic 'LS_COLORS=' in ':(top'

The loop runs for a second time after parsing "top", and copyfrom now
points to the byte after ":(top", which is coming from argv. And in my
distribution/platform, it looks like the envp, the third param of
main(), is packed right after the argv strings, because:
    $ env | head -n 1
    LS_COLORS=

Junio C Hamano· Mar 8, 2013, 01:51 UTC · re: Andrew Wong · lore

Re: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

Andrew Wong <andrew.kw.w@gmail.com> writes:

Show 11 quoted lines

> On 3/7/13, Junio C Hamano <gitster@pobox.com> wrote:
>> This did not error out for me, though.
>>
>>     $ cd t && git ls-files ":(top"
>
> No error message at all? Hm, maybe in your case, the byte after the
> end of string happens to be '\0' and the loop ended by chance?
>
> git doesn't crash for me, but it generates this error:
>     $ git ls-files ":(top"
>     fatal: Invalid pathspec magic 'LS_COLORS=' in ':(top'

What I meant was that I do not get any error _after_ applying your patch.

It is broken to behave as if "LS_COLORS=..." (which is totally unrelated string that happens to be laid out next in the memory) is a part of the pathspec magic specification your ":(top" started. Your patch makes the code stop doing that.

But it is equally broken to behave as if there is nothing wrong in the incomplete magic ":(top" that is not closed, isn't it?

Andrew Wong· Mar 8, 2013, 01:58 UTC · re: Junio C Hamano · lore

Re: [PATCH] setup.c: Fix prefix_pathspec from looping pass end of string

On 03/07/13 20:51, Junio C Hamano wrote:

> But it is equally broken to behave as if there is nothing wrong in
> the incomplete magic ":(top" that is not closed, isn't it?

Ah, yea, I did notice that, but then I saw a few lines below:
        if (*copyfrom == ')')
            copyfrom++;
which is explicitly making the ")" optional. So I thought maybe that was
the original intention, and left it at that. Though the doc says to end
with ")", so I guess it should error out after all? If that's the case,
I can try to come up with a patch to error it out (through die() ?).

Andrew Wong· Mar 9, 2013, 23:45 UTC · re: Junio C Hamano · lore

[PATCH 1/2] setup.c: Fix prefix_pathspec from looping pass end of string

The previous code was assuming length ends at either ")" or ",", and was not handling the case where strcspn returns length due to end of string. So specifying ":(top" as pathspec will cause the loop to go pass the end of string.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 setup.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Show changes to setup.c +4 −2

diff --git a/setup.c b/setup.c
index 1dee47e..f4c4e73 100644
--- a/setup.c
+++ b/setup.c
@@ -207,9 +207,11 @@ static const char *prefix_pathspec(const char *prefix, int prefixlen, const char
 		     *copyfrom && *copyfrom != ')';
 		     copyfrom = nextat) {
 			size_t len = strcspn(copyfrom, ",)");
-			if (copyfrom[len] == ')')
+			if (copyfrom[len] == '\0')
 				nextat = copyfrom + len;
-			else
+			else if (copyfrom[len] == ')')
+				nextat = copyfrom + len;
+			else if (copyfrom[len] == ',')
 				nextat = copyfrom + len + 1;
 			if (!len)
 				continue;

-- 
1.7.12.4

Andrew Wong· Mar 9, 2013, 23:46 UTC · re: Andrew Wong · lore

[PATCH 2/2] setup.c: Check that the pathspec magic ends with ")"

The previous code allowed the ")" to be optional.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 setup.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Show changes to setup.c +3 −2

diff --git a/setup.c b/setup.c
index f4c4e73..5ed2b93 100644
--- a/setup.c
+++ b/setup.c
@@ -225,8 +225,9 @@ static const char *prefix_pathspec(const char *prefix, int prefixlen, const char
 				die("Invalid pathspec magic '%.*s' in '%s'",
 				    (int) len, copyfrom, elt);
 		}
-		if (*copyfrom == ')')
-			copyfrom++;
+		if (*copyfrom != ')')
+			die("Missing ')' at the end of pathspec magic in '%s'", elt);
+		copyfrom++;
 	} else {
 		/* shorthand */
 		for (copyfrom = elt + 1;

-- 
1.7.12.4