do not read beyond end of malloc'd buffer
authorJim Meyering <jim@meyering.net>
Fri, 20 May 2011 17:20:12 +0000 (19:20 +0200)
committerJunio C Hamano <gitster@pobox.com>
Fri, 20 May 2011 18:39:49 +0000 (11:39 -0700)
commit42536dd9b9829b4eb4e3706e141b3c8bffa3e826
treedb640fa331f2b513c593eda286400c2086c9ec5a
parent5269edf1702b7375a287d5bbbb3c1b1f3a8aa765
do not read beyond end of malloc'd buffer

With diff.suppress-blank-empty=true, "git diff --word-diff" would
output data that had been read from uninitialized heap memory.
The problem was that fn_out_consume did not account for the
possibility of a line with length 1, i.e., the empty context line
that diff.suppress-blank-empty=true converts from " \n" to "\n".
Since it assumed there would always be a prefix character (the space),
it decremented "len" unconditionally, thus passing len=0 to emit_line,
which would then blindly call emit_line_0 with len=-1 which would
pass that value on to fwrite as SIZE_MAX.  Boom.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff.c
t/t4034-diff-words.sh