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use_pack: handle signed off_t overflow

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A v2 pack index file can specify an offset within a packfile
of up to 2^64-1 bytes. On a system with a signed 64-bit
off_t, we can represent only up to 2^63-1. This means that a
corrupted .idx file can end up with a negative offset in the
pack code. Our bounds-checking use_pack function looks for
too-large offsets, but not for ones that have wrapped around
to negative. Let's do so, which fixes an out-of-bounds
access demonstrated in t5313.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2016-02-25 09:23:26 -05:00 committed by Junio C Hamano
parent 47fe3f6ef0
commit 13e0b0d3dc
2 changed files with 3 additions and 1 deletions
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2
sha1_file.c
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@ -1041,6 +1041,8 @@ unsigned char *use_pack(struct packed_git *p,
die("packfile %s cannot be accessed", p->pack_name);
if (offset > (p->pack_size - 20))
die("offset beyond end of packfile (truncated pack?)");
if (offset < 0)
die("offset before end of packfile (broken .idx?)");
if (!win || !in_window(win, offset)) {
if (win)

2
t/t5313-pack-bounds-checks.sh
View File

@ -136,7 +136,7 @@ test_expect_success 'bogus offset into v2 extended table' '
test_must_fail git index-pack --verify $pack
'
test_expect_failure 'bogus offset inside v2 extended table' '
test_expect_success 'bogus offset inside v2 extended table' '
# We need two objects here, so we can plausibly require
# an extended table (if the first object were larger than 2^31).
do_pack "$object $(git rev-parse HEAD)" --index-version=2 &&