KASAN: use-after-free Read in process_preds

[syzbot]

Hello,

syzbot hit the following crash on bpf-next commit
5d1365940a68dd57b031b6e3c07d7d451cd69daf (Thu Apr 12 18:09:05 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=b6fc33dcecb65cd8ff80

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=4606019153952768
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-5947642240294114534
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

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Reported-by: syzbot+b6fc33dcecb65cd8ff80@xxxxxxxxxxxxxxxxxxxxxxxxx
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==================================================================
BUG: KASAN: use-after-free in predicate_parse  
kernel/trace/trace_events_filter.c:563 [inline]
BUG: KASAN: use-after-free in process_preds+0x197f/0x19b0  
kernel/trace/trace_events_filter.c:1505
Read of size 4 at addr ffff8801b9832ce4 by task syz-executor0/28463

CPU: 0 PID: 28463 Comm: syz-executor0 Not tainted 4.16.0+ #2
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:563 [inline]
 process_preds+0x197f/0x19b0 kernel/trace/trace_events_filter.c:1505
 create_filter+0x1a8/0x370 kernel/trace/trace_events_filter.c:1714
 ftrace_profile_set_filter+0x109/0x2b0  
kernel/trace/trace_events_filter.c:2042
 perf_event_set_filter+0x248/0x1230 kernel/events/core.c:9064
 _perf_ioctl+0x84c/0x15e0 kernel/events/core.c:5056
 perf_ioctl+0x59/0x80 kernel/events/core.c:5107
 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
 SYSC_ioctl fs/ioctl.c:708 [inline]
 SyS_ioctl+0x24/0x30 fs/ioctl.c:706
 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x455329
RSP: 002b:00007f14b2c73c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f14b2c746d4 RCX: 0000000000455329
RDX: 0000000020000040 RSI: 0000000040082406 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000291 R14: 00000000006f6e38 R15: 0000000000000000

Allocated by task 2370:
 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
 getname_flags+0xd0/0x5a0 fs/namei.c:140
 getname+0x19/0x20 fs/namei.c:211
 do_sys_open+0x39a/0x740 fs/open.c:1087
 SYSC_open fs/open.c:1111 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1106
 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 2370:
 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
 putname+0xf2/0x130 fs/namei.c:261
 do_sys_open+0x554/0x740 fs/open.c:1102
 SYSC_open fs/open.c:1111 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1106
 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801b9832340
 which belongs to the cache names_cache of size 4096
The buggy address is located 2468 bytes inside of
 4096-byte region [ffff8801b9832340, ffff8801b9833340)
The buggy address belongs to the page:
page:ffffea0006e60c80 count:1 mapcount:0 mapping:ffff8801b9832340 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801b9832340 0000000000000000 0000000100000001
raw: ffffea000743eca0 ffffea0006628f20 ffff8801dad86dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b9832b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801b9832c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801b9832c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8801b9832d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801b9832d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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