[x264-devel] AddressSanitizer: heap-buffer-overflow at encoder/me.c:406 with 4 threads

[Hongxu Chen]

Hi,

    I tested on the given patch, it does not crash any more on the poc file
(attached).
    I tried `./x264-fuzz/install/bin/x264 *--profile baseline* --threads 4
--quiet --output /dev/null $FILE' on *unpatched version* and it reports a
heap-buffer-overflow at me.c:244.
    With the patched version, this works fine.

Best Regards,
Hongxu


On Sat, Apr 13, 2019 at 4:22 AM BugMaster <BugMaster at narod.ru> wrote:

> On Tue, 9 Apr 2019 16:01:31 +0800, Hongxu Chen wrote:
> > Hi,
>
> >     On my machine, when running x264 with 4 threads (sandbox
> > version, git HEAD d4099dd4c722f52c4f3c14575d7d39eb8fadb97f), it may
> > cause a heap-buffer-overflow (read) at encoder/me.c:406.
>
>
> > $ ./x264-asan/install/bin/x264 --threads 4 --quiet --output /dev/null
> hbo_me.c:406_1
> > =================================================================
> > ==23250==ERROR: AddressSanitizer: heap-buffer-overflow on address
> > 0x621000030904 at pc 0x000000755471 bp 0x7fadac672df0 sp 0x7fadac672de8
> > READ of size 2 at 0x621000030904 thread T4
> >     #0 0x755470 in x264_8_me_search_ref
> > /home/hongxu/work/x264/x264-asan/encoder/me.c:406:13
> >     #1 0x6df538 in mb_analyse_inter_p16x16
> > /home/hongxu/work/x264/x264-asan/encoder/analyse.c:1275:13
> >     #2 0x6df538 in x264_8_macroblock_analyse
> > /home/hongxu/work/x264/x264-asan/encoder/analyse.c:3026
> >     #3 0x59f274 in slice_write
> > /home/hongxu/work/x264/x264-asan/encoder/encoder.c:2775:9
> >     #4 0x591bee in slices_write
> > /home/hongxu/work/x264/x264-asan/encoder/encoder.c:3116:13
> >     #5 0x5a9fdf in threadpool_thread_internal
> > /home/hongxu/work/x264/x264-asan/common/threadpool.c:69:20
> >     #6 0x5fefeb in x264_stack_align
> > (/home/hongxu/work/x264/x264-asan/install/bin/x264+0x5fefeb)
>
> > 0x621000030904 is located 2 bytes to the right of 4098-byte region
> [0x62100002f900,0x621000030902)
> > allocated by thread T0 here:
> >     #0 0x4d4948 in __interceptor_memalign.localalias.1
> > (/home/hongxu/work/x264/x264-asan/install/bin/x264+0x4d4948)
> >     #1 0x548fcc in x264_malloc
> > /home/hongxu/work/x264/x264-asan/common/base.c:124:21
>
> > Thread T4 created by T0 here:
> >     #0 0x4377a0 in pthread_create
> > (/home/hongxu/work/x264/x264-asan/install/bin/x264+0x4377a0)
> >     #1 0x5a96e9 in x264_8_threadpool_init
> > /home/hongxu/work/x264/x264-asan/common/threadpool.c:111:13
>
> > SUMMARY: AddressSanitizer: heap-buffer-overflow
> > /home/hongxu/work/x264/x264-asan/encoder/me.c:406:13 in
> x264_8_me_search_ref
> > Shadow bytes around the buggy address:
> >   0x0c427fffe0d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >   0x0c427fffe0e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >   0x0c427fffe0f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >   0x0c427fffe100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >   0x0c427fffe110: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> =>>0x0c427fffe120:[02]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> >   0x0c427fffe130: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> >   0x0c427fffe140: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> >   0x0c427fffe150: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> >   0x0c427fffe160: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> >   0x0c427fffe170: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> > Shadow byte legend (one shadow byte represents 8 application bytes):
> >   Addressable:           00
> >   Partially addressable: 01 02 03 04 05 06 07
> >   Heap left redzone:       fa
> >   Freed heap region:       fd
> >   Stack left redzone:      f1
> >   Stack mid redzone:       f2
> >   Stack right redzone:     f3
> >   Stack after return:      f5
> >   Stack use after scope:   f8
> >   Global redzone:          f9
> >   Global init order:       f6
> >   Poisoned by user:        f7
> >   Container overflow:      fc
> >   Array cookie:            ac
> >   Intra object redzone:    bb
> >   ASan internal:           fe
> >   Left alloca redzone:     ca
> >   Right alloca redzone:    cb
> > ==23250==ABORTING
> > [1]    23250 abort      ./x264-asan/install/bin/x264 --threads 4 --quiet
> --output /dev/null
>
> >   When running with 1,2,3 threads, it crashes at different places such
> as encoder/me.c:244.
> >   When running with 5 or more threads, everything seems fine.
>
> > Best Regards,
> > Hongxu
>
> Hi.
>
> Do this happen only with interlaced encoding?
> Can you test with attached patch. It should fix heap-buffer-overflow
> (read) with interlaced
> encoding._______________________________________________
> x264-devel mailing list
> x264-devel at videolan.org
> https://mailman.videolan.org/listinfo/x264-devel
>
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