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[ot-font] Fix hmtx table length checking, *again* 

Exactly the same problem that I fixed in
63ef0b41dc

I rewrote the table checking yesterday in
67f8821fb2
and introduced the exact same issue again. :(
Good thing we have ongoing fuzzing going now.  Was discovered
immediately by libFuzzer.  Thanks kcc!

https://github.com/behdad/harfbuzz/issues/139#issuecomment-153449473
Fixes https://github.com/behdad/harfbuzz/issues/156
This commit is contained in:
Behdad Esfahbod 2015-11-03 12:15:12 -08:00
parent 3530cc2d7c
commit df698f3299
4 changed files with 4 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/hb-ot-font.cc
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@ -59,11 +59,11 @@ struct hb_ot_face_metrics_accelerator_t
/* Cap num_metrics() and num_advances() based on table length. */
unsigned int len = hb_blob_get_length (this->blob);
if (unlikely (this->num_advances * 4 < len))
if (unlikely (this->num_advances * 4 > len))
this->num_advances = len / 4;
this->num_metrics = this->num_advances + (len - 4 * this->num_advances) / 2;
/* We MUSt set num_metrics to zero if num_advances is zero.
/* We MUST set num_metrics to zero if num_advances is zero.
* Our get_advance() depends on that. */
if (unlikely (!this->num_advances))
{

BIN
test/shaping/fonts/sha1sum/8240789f6d12d4cfc4b5e8e6f246c3701bcf861f.ttf Normal file
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Binary file not shown.

1
test/shaping/fonts/sha1sum/MANIFEST
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@ -17,6 +17,7 @@
757ebd573617a24aa9dfbf0b885c54875c6fe06b.ttf
7e14e7883ed152baa158b80e207b66114c823a8b.ttf
813c2f8e5512187fd982417a7fb4286728e6f4a8.ttf
8240789f6d12d4cfc4b5e8e6f246c3701bcf861f.ttf
8454d22037f892e76614e1645d066689a0200e61.ttf
8a9fea2a7384f2116e5b84a9b31f83be7850ce21.ttf
a919b33197965846f21074b24e30250d67277bce.ttf

1
test/shaping/tests/fuzzed.tests
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@ -3,3 +3,4 @@ fonts/sha1sum/5a5daf5eb5a4db77a2baa3ad9c7a6ed6e0655fa8.ttf:--font-funcs=ot:U+004
fonts/sha1sum/0509e80afb379d16560e9e47bdd7d888bebdebc6.ttf:--font-funcs=ot:U+0041:[gid0=0+1000]
fonts/sha1sum/641bd9db850193064d17575053ae2bf8ec149ddc.ttf:--font-funcs=ot:U+0041:[gid0=0+1000]
fonts/sha1sum/375d6ae32a3cbe52fbf81a4e5777e3377675d5a3.ttf:--font-funcs=ot:U+0041:[gid0=0+4352]
fonts/sha1sum/8240789f6d12d4cfc4b5e8e6f246c3701bcf861f.ttf:--font-funcs=ot:U+0041:[gid0=0+2304]