threads / bug / 56438

[BUG?] git range-diff -Ix @{1}... segfaults

Subject: [BUG?] git range-diff -Ix @{1}... segfaults

## tl;dr

3 messages between Sep 3, 2021 and Sep 7, 2021.

replies: 2people: 2as markdown or json

Junio C Hamano· Sep 3, 2021, 18:49 UTC · lore

It does not seem to trigger with an empty range, e.g.

    $ git range-diff -Ix HEAD...
    $ git range-diff -Ix HEAD~...
    -:  ---------- > 1:  0a0bc7d03a scalar: accept -C and -c opt...

but when it needs real comparison, the -I seems to kill the command quite easily.

THanks.

René Scharfe· Sep 4, 2021, 07:50 UTC · re: Junio C Hamano · lore

Re: [BUG?] git range-diff -Ix @{1}... segfaults

Am 03.09.21 um 20:49 schrieb Junio C Hamano:

Show 8 quoted lines

> It does not seem to trigger with an empty range, e.g.
>
>     $ git range-diff -Ix HEAD...
>     $ git range-diff -Ix HEAD~...
>     -:  ---------- > 1:  0a0bc7d03a scalar: accept -C and -c opt...
>
> but when it needs real comparison, the -I seems to kill the command
> quite easily.

Reverting c45dc9cf30 (diff: plug memory leak from regcomp() on {log,diff} -I, 2021-02-11) fixes the segfault.

diff.c::diff_free() frees the ignore_regex member of a struct diff_options, but doesn't reset the ignore_regex_nr nor clears the pointer. It is called from diff.c::diff_flush().

range-diff.c::output() calls diff.c::diff_flush() in a loop with the same struct diff_options (via range-diff.c::patch_diff()).

So the second iteration of that loop tries to use the already freed ignore regexes. Here's a patch for that:

--- >8 ---
Subject: [PATCH] range-diff: avoid segfault with -I

output() reuses the same struct diff_options for multiple calls of diff_flush(). Set the option no_free to instruct it to keep the ignore regexes between calls and release them explicitly at the end.

Signed-off-by: René Scharfe <l.s.r@web.de>
---
Test missing because I couldn't see any effect of -I on range-diff.

 range-diff.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/range-diff.c b/range-diff.c
index e731525e66..cac89a2f4f 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -482,6 +482,7 @@ static void output(struct string_list *a, struct string_list *b,
 	else
 		diff_setup(&opts);

+	opts.no_free = 1;
 	if (!opts.output_format)
 		opts.output_format = DIFF_FORMAT_PATCH;
 	opts.flags.suppress_diff_headers = 1;
@@ -542,6 +543,8 @@ static void output(struct string_list *a, struct string_list *b,
 	strbuf_release(&buf);
 	strbuf_release(&dashes);
 	strbuf_release(&indent);
+	opts.no_free = 0;
+	diff_free(&opts);
 }

 int show_range_diff(const char *range1, const char *range2,
--
2.33.0

Junio C Hamano· Sep 7, 2021, 20:05 UTC · re: René Scharfe · lore

Re: [BUG?] git range-diff -Ix @{1}... segfaults

René Scharfe <l.s.r@web.de> writes:

> range-diff.c::output() calls diff.c::diff_flush() in a loop with the
> same struct diff_options (via range-diff.c::patch_diff()).

Woooo, that's, eh, unexpected.

> So the second iteration of that loop tries to use the already freed
> ignore regexes.  Here's a patch for that:

Thanks.

Show 11 quoted lines

>
> --- >8 ---
> Subject: [PATCH] range-diff: avoid segfault with -I
>
> output() reuses the same struct diff_options for multiple calls of
> diff_flush().  Set the option no_free to instruct it to keep the
> ignore regexes between calls and release them explicitly at the end.
>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
> Test missing because I couldn't see any effect of -I on range-diff.

I wanted to omit my sign-off when comparing a previous series and the new series (iow, I expected -I"^Signed-off-by: me" to apply to the outer diff, not the inner "generation of patches to be compared").

Show 26 quoted lines

>  range-diff.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/range-diff.c b/range-diff.c
> index e731525e66..cac89a2f4f 100644
> --- a/range-diff.c
> +++ b/range-diff.c
> @@ -482,6 +482,7 @@ static void output(struct string_list *a, struct string_list *b,
>  	else
>  		diff_setup(&opts);
>
> +	opts.no_free = 1;
>  	if (!opts.output_format)
>  		opts.output_format = DIFF_FORMAT_PATCH;
>  	opts.flags.suppress_diff_headers = 1;
> @@ -542,6 +543,8 @@ static void output(struct string_list *a, struct string_list *b,
>  	strbuf_release(&buf);
>  	strbuf_release(&dashes);
>  	strbuf_release(&indent);
> +	opts.no_free = 0;
> +	diff_free(&opts);
>  }
>
>  int show_range_diff(const char *range1, const char *range2,
> --
> 2.33.0