general protection fault in afs_dynroot_depopulate

[syzbot <syzbot+c1eff8205244ae7e11a6@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    18445bf4 Merge tag 'spi-fix-v5.9-rc1' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ff6f29900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a0437fdd630bee11
dashboard link: https://syzkaller.appspot.com/bug?extid=c1eff8205244ae7e11a6
compiler:       gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c1eff8205244ae7e11a6@syzkaller.appspotmail.com

RSP: 002b:00007fd9b2daca88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fd9b2dacb20 RCX: 000000000045ff2a
RDX: 0000000020000040 RSI: 0000000020000080 RDI: 0000000000000000
RBP: 00007fd9b2dacae0 R08: 00007fd9b2dacb20 R09: 0000000020000040
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000020000040
R13: 0000000020000080 R14: 0000000000000000 R15: 0000000020000000
general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 0 PID: 26047 Comm: syz-executor.3 Not tainted 5.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:afs_dynroot_depopulate+0x25f/0x529 fs/afs/dynroot.c:385
Code: 00 00 0f 84 5c 01 00 00 e8 2e a5 ae fe 4d 8d 7e 68 48 89 ef e8 02 70 2f 05 4c 89 fa 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 02 00 00 49 8b 46 68 4d 8d ae 18 01 00 00 48
RSP: 0018:ffffc90015fa7ca0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88809edfc000 RCX: 1ffff92002bf4f81
RDX: 000000000000000d RSI: 0000000000000008 RDI: ffff88809dd392c0
RBP: ffff88809dd392c0 R08: 0000000000000001 R09: ffff88809dd392c7
R10: ffffed1013ba7258 R11: 0000000000000001 R12: ffff88809dd39000
R13: ffff8880a650b800 R14: 0000000000000000 R15: 0000000000000068
FS:  00007fd9b2dad700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000016a1000 CR3: 000000008eb1d000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 afs_kill_super+0x13b/0x180 fs/afs/super.c:535
 deactivate_locked_super+0x94/0x160 fs/super.c:335
 afs_get_tree+0x1124/0x1460 fs/afs/super.c:598
 vfs_get_tree+0x89/0x2f0 fs/super.c:1547
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x1387/0x2070 fs/namespace.c:3192
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount fs/namespace.c:3390 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45ff2a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 da 89 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fd9b2daca88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fd9b2dacb20 RCX: 000000000045ff2a
RDX: 0000000020000040 RSI: 0000000020000080 RDI: 0000000000000000
RBP: 00007fd9b2dacae0 R08: 00007fd9b2dacb20 R09: 0000000020000040
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000020000040
R13: 0000000020000080 R14: 0000000000000000 R15: 0000000020000000
Modules linked in:
---[ end trace d330bd77c4cff0f5 ]---
RIP: 0010:afs_dynroot_depopulate+0x25f/0x529 fs/afs/dynroot.c:385
Code: 00 00 0f 84 5c 01 00 00 e8 2e a5 ae fe 4d 8d 7e 68 48 89 ef e8 02 70 2f 05 4c 89 fa 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 02 00 00 49 8b 46 68 4d 8d ae 18 01 00 00 48
RSP: 0018:ffffc90015fa7ca0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88809edfc000 RCX: 1ffff92002bf4f81
RDX: 000000000000000d RSI: 0000000000000008 RDI: ffff88809dd392c0
RBP: ffff88809dd392c0 R08: 0000000000000001 R09: ffff88809dd392c7
R10: ffffed1013ba7258 R11: 0000000000000001 R12: ffff88809dd39000
R13: ffff8880a650b800 R14: 0000000000000000 R15: 0000000000000068
FS:  00007fd9b2dad700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000016a1000 CR3: 000000008eb1d000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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