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

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    af5136f9 selftests/net: SO_TXTIME with ETF and FQ
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13164ee4a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fc045131472947d7
dashboard link: https://syzkaller.appspot.com/bug?extid=3d04999521633dceb439
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1661b6e4a00000

Bisection is inconclusive: the first bad commit could be any of:

7c00e8ae Merge tag 'armsoc-soc' of  
git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
a2b7ab45 Merge tag 'linux-watchdog-4.18-rc1' of  
git://www.linux-watchdog.org/linux-watchdog
721afaa2 Merge tag 'armsoc-dt' of  
git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1062daaaa00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3d04999521633dceb439@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in class_equal+0x40/0x50  
kernel/locking/lockdep.c:1527
Read of size 8 at addr ffff8880813cdab0 by task syz-executor.0/9147

CPU: 0 PID: 9147 Comm: syz-executor.0 Not tainted 5.2.0-rc1+ #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:

Allocated by task 2266519551:
------------[ cut here ]------------
kernel BUG at mm/slab.c:4178!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9147 Comm: syz-executor.0 Not tainted 5.2.0-rc1+ #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__check_heap_object+0xa5/0xb3 mm/slab.c:4178
Code: 2b 48 c7 c7 4d fc 61 88 e8 28 ad 07 00 5d c3 41 8b 91 04 01 00 00 48  
29 c7 48 39 d7 77 bd 48 01 d0 48 29 c8 4c 39 c0 72 b2 c3 <0f> 0b 48 c7 c7  
4d fc 61 88 e8 3c b2 07 00 44 89 e1 48 c7 c7 08 fd
RSP: 0018:ffff8880813cd370 EFLAGS: 00010046
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 000000000000000c
RDX: ffff8880813cc340 RSI: 0000000000000000 RDI: ffff8880813cd468
RBP: ffff8880813cd3c0 R08: 0000000000000001 R09: ffff8880aa594c40
R10: 0000000000000f23 R11: 0000000000000000 R12: ffff8880813cd468
R13: ffffea000204f300 R14: ffff8880813cd469 R15: 0000000000000001
FS:  00005555564e1940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff8c046bd8 CR3: 000000009a952000 CR4: 00000000001406f0
Call Trace:
Modules linked in:
---[ end trace e78aeeb619bc791b ]---
RIP: 0010:__check_heap_object+0xa5/0xb3 mm/slab.c:4178
Code: 2b 48 c7 c7 4d fc 61 88 e8 28 ad 07 00 5d c3 41 8b 91 04 01 00 00 48  
29 c7 48 39 d7 77 bd 48 01 d0 48 29 c8 4c 39 c0 72 b2 c3 <0f> 0b 48 c7 c7  
4d fc 61 88 e8 3c b2 07 00 44 89 e1 48 c7 c7 08 fd
RSP: 0018:ffff8880813cd370 EFLAGS: 00010046
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 000000000000000c
RDX: ffff8880813cc340 RSI: 0000000000000000 RDI: ffff8880813cd468
RBP: ffff8880813cd3c0 R08: 0000000000000001 R09: ffff8880aa594c40
R10: 0000000000000f23 R11: 0000000000000000 R12: ffff8880813cd468
R13: ffffea000204f300 R14: ffff8880813cd469 R15: 0000000000000001
FS:  00005555564e1940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff8c046bd8 CR3: 000000009a952000 CR4: 00000000001406f0


---
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