On 14.12.2015 00:51, Michael Niedermayer wrote: > On Sun, Dec 13, 2015 at 09:56:06PM +0100, Andreas Cadhalpun wrote: >> Also correct the check to reject log < 7, because UPDATE_CACHE only >> guarantees 25 meaningful bits. >> >> This fixes undefined behavior: >> runtime error: shift exponent is negative >> >> Testing with START/STOP timers in get_ue_golomb, one for the first >> branch (A) and one for the second (B), shows that there is practically no >> slowdown, e.g. for the cavs decoder: >> >> With the check in the B branch: >> 629 decicycles in get_ue_golomb B, 4194260 runs, 44 skips >> 433 decicycles in get_ue_golomb A,268434102 runs, 1354 skips >> >> Without the check: >> 624 decicycles in get_ue_golomb B, 4194273 runs, 31 skips >> 433 decicycles in get_ue_golomb A,268434203 runs, 1253 skips >> >> Since the B branch is executed far less often than the A branch, this >> change is negligible, even more so for the h264 decoder, where the ratio >> B/A is a lot smaller. >> >> Fixes: mozilla bug 1229208 >> Fixes: >> fbeb8b2c7c996e9b91c6b1af319d7ebc/asan_heap-oob_195450f_2743_e8856ece4579ea486670be2b236099a0.bit >> >> Found-by: Tyson Smith >> Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind >> Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> >> --- >> >> Note that I just copied the "Fixes:" lines from Michael's patch, but actually >> I don't know what mozilla bug 1229208 is about, as it seems not to be public. >> Also I don't have the mentioned sample, but the patch fixes more than 1000 >> of my fuzzed samples that triggered this ubsan error, so I'm confident the >> mentioned one is also fixed. > > actually i think the bug number is > "Bug 1230239 - FFMPEG: shift exponent is negative in [@get_ue_golomb] "
I changed the bug number accordingly, > patch should be ok and pushed the patch. > and iam also not happy about the bugs being non public > i tried unchecking "Security-Sensitive Media Bug" but i seem not to > have the power to do that but its quite possibly iam doing something > wrong Maybe add a comment requesting the bug to be made public, so that someone who has that power can do it. Best regards, Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel