KASAN: slab-out-of-bounds Read in process_preds

From: syzbot
Date: Fri Apr 27 2018 - 01:30:50 EST

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Hello,

syzbot hit the following crash on bpf-next commit
af487c5777709d4b7f874fe1a33f9289d51b9adc (Wed Apr 25 07:56:11 2018 +0000)
Merge branch 'bpf-optimize-neg-sums'
syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=e47d942a98e75b4bd03e

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output: https://syzkaller.appspot.com/x/log.txt?id=5744539889303552
Kernel config: https://syzkaller.appspot.com/x/.config?id=-2918904850634584293
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e47d942a98e75b4bd03e@xxxxxxxxxxxxxxxxxxxxxxxxx
It will help syzbot understand when the bug is fixed. See footer for details.
If you forward the report, please keep this part and the footer.

==================================================================
BUG: KASAN: slab-out-of-bounds in predicate_parse kernel/trace/trace_events_filter.c:562 [inline]
BUG: KASAN: slab-out-of-bounds in process_preds+0x196f/0x19b0 kernel/trace/trace_events_filter.c:1505
Read of size 4 at addr ffff8801b2b55ff0 by task syz-executor7/7974

CPU: 1 PID: 7974 Comm: syz-executor7 Not tainted 4.17.0-rc1+ #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
predicate_parse kernel/trace/trace_events_filter.c:562 [inline]
process_preds+0x196f/0x19b0 kernel/trace/trace_events_filter.c:1505
create_filter+0x155/0x270 kernel/trace/trace_events_filter.c:1713
ftrace_profile_set_filter+0x130/0x2e0 kernel/trace/trace_events_filter.c:2038
perf_event_set_filter+0x248/0x1230 kernel/events/core.c:9075
_perf_ioctl+0x84c/0x15e0 kernel/events/core.c:5059
perf_ioctl+0x59/0x80 kernel/events/core.c:5110
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
__do_sys_ioctl fs/ioctl.c:708 [inline]
__se_sys_ioctl fs/ioctl.c:706 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455389
RSP: 002b:00007f63bbd38c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f63bbd396d4 RCX: 0000000000455389
RDX: 0000000020000040 RSI: 0000000040082406 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000029a R14: 00000000006f6f10 R15: 0000000000000000

Allocated by task 6559:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
anon_vma_chain_alloc mm/rmap.c:128 [inline]
anon_vma_clone+0x138/0x720 mm/rmap.c:268
anon_vma_fork+0xe8/0x950 mm/rmap.c:331
dup_mmap kernel/fork.c:468 [inline]
dup_mm kernel/fork.c:1235 [inline]
copy_mm kernel/fork.c:1289 [inline]
copy_process.part.38+0x2f21/0x6e90 kernel/fork.c:1795
copy_process kernel/fork.c:1608 [inline]
_do_fork+0x291/0x12a0 kernel/fork.c:2089
__do_sys_clone kernel/fork.c:2196 [inline]
__se_sys_clone kernel/fork.c:2190 [inline]
__x64_sys_clone+0xbf/0x150 kernel/fork.c:2190
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7294:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
anon_vma_chain_free mm/rmap.c:133 [inline]
unlink_anon_vmas+0x3aa/0xa40 mm/rmap.c:400
free_pgtables+0x271/0x380 mm/memory.c:641
exit_mmap+0x2ca/0x570 mm/mmap.c:3057
__mmput kernel/fork.c:962 [inline]
mmput+0x251/0x610 kernel/fork.c:983
exec_mmap fs/exec.c:1044 [inline]
flush_old_exec+0xb94/0x20e0 fs/exec.c:1276
load_elf_binary+0xa33/0x5610 fs/binfmt_elf.c:869
search_binary_handler+0x17d/0x570 fs/exec.c:1653
exec_binprm fs/exec.c:1695 [inline]
do_execveat_common.isra.34+0x16ce/0x2590 fs/exec.c:1817
do_execve fs/exec.c:1862 [inline]
__do_sys_execve fs/exec.c:1943 [inline]
__se_sys_execve fs/exec.c:1938 [inline]
__x64_sys_execve+0x8d/0xb0 fs/exec.c:1938
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801b2b55f60
which belongs to the cache anon_vma_chain of size 64
The buggy address is located 80 bytes to the right of
64-byte region [ffff8801b2b55f60, ffff8801b2b55fa0)
The buggy address belongs to the page:
page:ffffea0006cad540 count:1 mapcount:0 mapping:ffff8801b2b55000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801b2b55000 0000000000000000 000000010000002a
raw: ffffea0006a72060 ffffea0006f615e0 ffff8801da94a500 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801b2b55e80: fc fc fc fc fb fb fb fb fb fb fb fb fc fc fc fc
ffff8801b2b55f00: fb fb fb fb fb fb fb fb fc fc fc fc fb fb fb fb

ffff8801b2b55f80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc

^
ffff8801b2b56000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801b2b56080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
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Next message: Christoph Hellwig: "Re: [LSF/MM TOPIC NOTES] x86 ZONE_DMA love"
Previous message: syzbot: "KASAN: use-after-free Read in process_preds"
Next in thread: Dmitry Vyukov: "Re: KASAN: slab-out-of-bounds Read in process_preds"
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