| commit | 46d723ce57f2dd3c50504dc6f4ca73b4c392fa6f | [log] [tgz] |
|---|---|---|
| author | Jeff King <peff@peff.net> | Mon Aug 09 21:01:52 2021 -0400 |
| committer | Junio C Hamano <gitster@pobox.com> | Tue Aug 10 11:38:13 2021 -0700 |
| tree | 1518e7fc1d64be9eb10cf8e2ca48527b49fc36b9 | |
| parent | c753e2a7a8e81c646611e808ce3b7a68f6e90add [diff] |
apply: keep buffer/size pair in sync when parsing binary hunks
We parse through binary hunks by looping through the buffer with code
like:
llen = linelen(buffer, size);
...do something with the line...
buffer += llen;
size -= llen;
However, before we enter the loop, there is one call that increments
"buffer" but forgets to decrement "size". As a result, our "size" is off
by the length of that line, and subsequent calls to linelen() may look
past the end of the buffer for a newline.
The fix is easy: we just need to decrement size as we do elsewhere.
This bug goes all the way back to 0660626caf (binary diff: further
updates., 2006-05-05). Presumably nobody noticed because it only
triggers if the patch is corrupted, and even then we are often "saved"
by luck. We use a strbuf to store the incoming patch, so we overallocate
there, plus we add a 16-byte run of NULs as slop for memory comparisons.
So if this happened accidentally, the common case is that we'd just read
a few uninitialized bytes from the end of the strbuf before producing
the expected "this patch is corrupted" error complaint.
However, it is possible to carefully construct a case which reads off
the end of the buffer. The included test does so. It will pass both
before and after this patch when run normally, but using a tool like
ASan shows that we get an out-of-bounds read before this patch, but not
after.
Reported-by: Xingman Chen <xichixingman@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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