From fc5589d6c1200f87689ff95067f18caa2a826382 Mon Sep 17 00:00:00 2001 From: Derrick Stolee Date: Thu, 3 Oct 2024 11:58:42 +0000 Subject: [PATCH] line-log: protect inner strbuf from free The output_prefix() method in line-log.c may call a function pointer via the diff_options struct. This function pointer returns a strbuf struct and then its buffer is passed back. However, that implies that the consumer is responsible to free the string. This is especially true because the default behavior is to duplicate the empty string. The existing functions used in the output_prefix pointer include: 1. idiff_prefix_cb() in diff-lib.c. This returns the data pointer, so the value exists across multiple calls. 2. diff_output_prefix_callback() in graph.c. This uses a static strbuf struct, so it reuses buffers across calls. These should not be freed. 3. output_prefix_cb() in range-diff.c. This is similar to the diff-lib.c case. In each case, we should not be freeing this buffer. We can convert the output_prefix() function to return a const char pointer and stop freeing the result. This choice is essentially the opposite of what was done in 394affd46d (line-log: always allocate the output prefix, 2024-06-07). This was discovered via 'valgrind' while investigating a public report of a bug in 'git log --graph -L' [1]. [1] https://github.com/git-for-windows/git/issues/5185 This issue would have been caught by the new test, when Git is compiled with ASan to catch these double frees. Co-authored-by: Jeff King Signed-off-by: Jeff King Signed-off-by: Derrick Stolee Signed-off-by: Junio C Hamano --- line-log.c | 10 ++++------ t/t4211-line-log.sh | 28 ++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+), 6 deletions(-) diff --git a/line-log.c b/line-log.c index 67c80b39a0..29cf66bdd1 100644 --- a/line-log.c +++ b/line-log.c @@ -897,13 +897,13 @@ static void print_line(const char *prefix, char first, fputs("\\ No newline at end of file\n", file); } -static char *output_prefix(struct diff_options *opt) +static const char *output_prefix(struct diff_options *opt) { if (opt->output_prefix) { struct strbuf *sb = opt->output_prefix(opt, opt->output_prefix_data); return sb->buf; } else { - return xstrdup(""); + return ""; } } @@ -916,7 +916,7 @@ static void dump_diff_hacky_one(struct rev_info *rev, struct line_log_data *rang struct diff_ranges *diff = &range->diff; struct diff_options *opt = &rev->diffopt; - char *prefix = output_prefix(opt); + const char *prefix = output_prefix(opt); const char *c_reset = diff_get_color(opt->use_color, DIFF_RESET); const char *c_frag = diff_get_color(opt->use_color, DIFF_FRAGINFO); const char *c_meta = diff_get_color(opt->use_color, DIFF_METAINFO); @@ -1003,7 +1003,6 @@ static void dump_diff_hacky_one(struct rev_info *rev, struct line_log_data *rang out: free(p_ends); free(t_ends); - free(prefix); } /* @@ -1012,10 +1011,9 @@ out: */ static void dump_diff_hacky(struct rev_info *rev, struct line_log_data *range) { - char *prefix = output_prefix(&rev->diffopt); + const char *prefix = output_prefix(&rev->diffopt); fprintf(rev->diffopt.file, "%s\n", prefix); - free(prefix); while (range) { dump_diff_hacky_one(rev, range); diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh index 02d76dca28..950451cf6a 100755 --- a/t/t4211-line-log.sh +++ b/t/t4211-line-log.sh @@ -337,4 +337,32 @@ test_expect_success 'zero-width regex .* matches any function name' ' test_cmp expect actual ' +test_expect_success 'show line-log with graph' ' + qz_to_tab_space >expect <<-EOF && + * $head_oid Modify func2() in file.c + |Z + | diff --git a/file.c b/file.c + | --- a/file.c + | +++ b/file.c + | @@ -6,4 +6,4 @@ + | int func2() + | { + | - return F2; + | + return F2 + 2; + | } + * $root_oid Add func1() and func2() in file.c + ZZ + diff --git a/file.c b/file.c + --- /dev/null + +++ b/file.c + @@ -0,0 +6,4 @@ + +int func2() + +{ + + return F2; + +} + EOF + git log --graph --oneline -L:func2:file.c >actual && + test_cmp expect actual +' + test_done