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patch 9.1.1567: crash when using inline diff mode

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Problem:  Crash when using inline diff mode
          (Ilya Grigoriev)
Solution: Set tp_diffbuf to NULL when skipping a diff block
          (Yee Cheng Chin).

Fix an array out of bounds crash when using diffopt+=inline:char when 4
or more buffers are being diff'ed. This happens when one of the blocks
is empty. The inline highlight logic skips using that buffer's block,
but when another buffer is used later and calls diff_read() to merge the
diff blocks together, it could erroneously consider the empty block's
diff info which has not been initialized, leaving to diff numbers that
are invalid. Later on the diff num is used without bounds checking which
leads to the crash.

Fix this by making sure to unset tp_diffbuf to NULL when we skip a
block, so diff_read() will not consider this buffer to be used within
inline diff. Also, add more bounds checking just to be safe.

closes: #17805

Signed-off-by: Yee Cheng Chin <ychin.git@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
This commit is contained in:
Yee Cheng Chin
2025-07-20 09:19:13 +02:00
committed by Christian Brabandt
parent 0e40501a9d
commit c8b99e2d13
4 changed files with 51 additions and 2 deletions
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15
src/diff.c
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@ -3391,6 +3391,11 @@ diff_find_change_inline_diff(
diff_T *orig_diff = curtab->tp_first_diff;
curtab->tp_first_diff = NULL;
// diff_read() also uses curtab->tp_diffbuf to determine what's an active
// buffer
buf_T *(orig_diffbuf[DB_COUNT]);
memcpy(orig_diffbuf, curtab->tp_diffbuf, sizeof(orig_diffbuf));
// Buffers to populate mmfile 1/2 that would be passed to xdiff as memory
// files. Use a grow array as it is not obvious how much exact space we
// need.
@ -3412,7 +3417,12 @@ diff_find_change_inline_diff(
continue; // skip buffer that isn't loaded
if (dp->df_count[i] == 0)
continue; // skip buffer that don't have any texts in this block
{
// skip buffers that don't have any texts in this block so we don't
// end up marking the entire block as modified in multi-buffer diff
curtab->tp_diffbuf[i] = NULL;
continue;
}
if (file1_idx == -1)
file1_idx = i;
@ -3626,7 +3636,7 @@ diff_find_change_inline_diff(
CLEAR_FIELD(change);
for (int i = 0; i < DB_COUNT; i++)
{
if (new_diff->df_lnum[i] == 0)
if (new_diff->df_lnum[i] <= 0) // should never be < 0. Checking just for safety.
continue;
linenr_T diff_lnum = new_diff->df_lnum[i] - 1; // use zero-index
linenr_T diff_lnum_end = diff_lnum + new_diff->df_count[i];
@ -3675,6 +3685,7 @@ done:
diff_clear(curtab);
curtab->tp_first_diff = orig_diff;
memcpy(curtab->tp_diffbuf, orig_diffbuf, sizeof(orig_diffbuf));
ga_clear(&file1_str);
ga_clear(&file2_str);