BUG: unable to handle kernel NULL pointer dereference in qlink_free

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b3a60822 Merge branch 'for-v5.6' of git://git.kernel.org:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13ea4a79e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5766bb49c0bc43b9
dashboard link: https://syzkaller.appspot.com/bug?extid=76833d0f66a9ec726366
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
CC: [jmo...@namei.org linux-...@vger.kernel.org linux-secu...@vger.kernel.org penguin...@I-love.SAKURA.ne.jp se...@hallyn.com take...@nttdata.co.jp]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+76833d...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000134
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 5d73b067 P4D 5d73b067 PUD 5d73a067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 2971 Comm: udevd Not tainted 5.5.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:qlink_free+0x1a/0xb0 arch/x86/include/asm/paravirt.h:747
Code: 7c a7 a7 ff 48 83 c4 08 5d c3 66 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 53 48 83 3d b7 c3 76 07 00 0f 84 86 00 00 00 49 89 f7 <48> 63 8e 34 01 00 00 9c 58 0f 1f 44 00 00 48 83 3d a8 c3 76 07 00
RSP: 0018:ffffc900016a7868 EFLAGS: 00010286
RAX: ffffea0000000000 RBX: f000ff53f000ff53 RCX: ffffea0000000008
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888000000000
RBP: ffffc900016a7880 R08: ffffffff81361eb0 R09: ffffed10154bfbc1
R10: ffffed10154bfbc1 R11: 0000000000000000 R12: ffff888000000000
R13: 0000000000001000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007effd30717a0(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000134 CR3: 000000004e974000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
qlist_free_all mm/kasan/quarantine.c:167 [inline]
quarantine_reduce+0x15c/0x1d0 mm/kasan/quarantine.c:260
__kasan_kmalloc+0x43/0x1c0 mm/kasan/common.c:494
kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:521
slab_post_alloc_hook mm/slab.h:584 [inline]
slab_alloc mm/slab.c:3320 [inline]
__do_kmalloc mm/slab.c:3654 [inline]
__kmalloc+0x22b/0x340 mm/slab.c:3665
kmalloc include/linux/slab.h:561 [inline]
tomoyo_realpath_from_path+0xe8/0x6b0 security/tomoyo/realpath.c:252
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x192/0x850 security/tomoyo/file.c:822
tomoyo_inode_getattr+0x1c/0x20 security/tomoyo/tomoyo.c:129
security_inode_getattr+0xc0/0x140 security/security.c:1254
vfs_getattr+0x2a/0x6d0 fs/stat.c:115
vfs_statx_fd fs/stat.c:145 [inline]
vfs_fstat include/linux/fs.h:3265 [inline]
__do_sys_newfstat fs/stat.c:378 [inline]
__se_sys_newfstat fs/stat.c:375 [inline]
__x64_sys_newfstat+0xa3/0x130 fs/stat.c:375
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7effd2778cb4
Code: 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 90 90 90 90 90 90 90 90 90 83 ff 01 89 f0 77 19 48 63 f8 48 89 d6 b8 05 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 18 f3 c3 66 90 48 8b 05 51 51 2b 00 64 c7 00
RSP: 002b:00007ffc8893f2e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000005
RAX: ffffffffffffffda RBX: 00000000018f82b0 RCX: 00007effd2778cb4
RDX: 00007ffc8893f2f0 RSI: 00007ffc8893f2f0 RDI: 0000000000000005
RBP: 0000000000003fff R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000a
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffc8893f870
Modules linked in:
CR2: 0000000000000134
---[ end trace 57b5175663ca1ab3 ]---
RIP: 0010:qlink_free+0x1a/0xb0 arch/x86/include/asm/paravirt.h:747
Code: 7c a7 a7 ff 48 83 c4 08 5d c3 66 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 53 48 83 3d b7 c3 76 07 00 0f 84 86 00 00 00 49 89 f7 <48> 63 8e 34 01 00 00 9c 58 0f 1f 44 00 00 48 83 3d a8 c3 76 07 00
RSP: 0018:ffffc900016a7868 EFLAGS: 00010286
RAX: ffffea0000000000 RBX: f000ff53f000ff53 RCX: ffffea0000000008
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888000000000
RBP: ffffc900016a7880 R08: ffffffff81361eb0 R09: ffffed10154bfbc1
R10: ffffed10154bfbc1 R11: 0000000000000000 R12: ffff888000000000
R13: 0000000000001000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007effd30717a0(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000134 CR3: 000000004e974000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.