general protection fault in security_inode_getattr

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    d012a719 Linux 5.9-rc2
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14aa130e900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=891ca5711a9f1650
dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=104a650e900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f07cc9be8d1d226947ed at syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 1 PID: 32288 Comm: syz-executor.3 Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:d_backing_inode include/linux/dcache.h:549 [inline]
RIP: 0010:security_inode_getattr+0x42/0x140 security/security.c:1276
Code: 1b fe 49 8d 5e 08 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 bc b4 5b fe 48 8b 1b 48 83 c3 68 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 9f b4 5b fe 48 8b 1b 48 83 c3 0c
RSP: 0018:ffffc9000a017750 EFLAGS: 00010202
RAX: 000000000000000d RBX: 0000000000000068 RCX: ffff888093ec6180
RDX: 0000000000000000 RSI: ffffc9000a017860 RDI: ffffc9000a017850
RBP: ffffc9000a017850 R08: dffffc0000000000 R09: ffffc9000a017850
R10: fffff52001402f0c R11: 0000000000000000 R12: ffffc9000a017860
R13: 0000000000008401 R14: ffffc9000a017850 R15: dffffc0000000000
FS:  00007f292d4ef700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30920074 CR3: 00000000937fd000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vfs_getattr+0x21/0x60 fs/stat.c:121
 ovl_copy_up_one fs/overlayfs/copy_up.c:850 [inline]
 ovl_copy_up_flags+0x2ef/0x2a00 fs/overlayfs/copy_up.c:931
 ovl_maybe_copy_up+0x154/0x180 fs/overlayfs/copy_up.c:963
 ovl_open+0xa2/0x200 fs/overlayfs/file.c:147
 do_dentry_open+0x7c8/0x1010 fs/open.c:817
 do_open fs/namei.c:3251 [inline]
 path_openat+0x2794/0x3840 fs/namei.c:3368
 do_filp_open+0x191/0x3a0 fs/namei.c:3395
 file_open_name+0x321/0x430 fs/open.c:1113
 acct_on kernel/acct.c:207 [inline]
 __do_sys_acct kernel/acct.c:286 [inline]
 __se_sys_acct+0x122/0x6f0 kernel/acct.c:273
 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d579
Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f292d4eec78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3
RAX: ffffffffffffffda RBX: 0000000000000700 RCX: 000000000045d579
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
RBP: 000000000118cf70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffc8e04bc4f R14: 00007f292d4ef9c0 R15: 000000000118cf4c
Modules linked in:
---[ end trace 7e4f1041b188e411 ]---
RIP: 0010:d_backing_inode include/linux/dcache.h:549 [inline]
RIP: 0010:security_inode_getattr+0x42/0x140 security/security.c:1276
Code: 1b fe 49 8d 5e 08 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 bc b4 5b fe 48 8b 1b 48 83 c3 68 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 9f b4 5b fe 48 8b 1b 48 83 c3 0c
RSP: 0018:ffffc9000a017750 EFLAGS: 00010202
RAX: 000000000000000d RBX: 0000000000000068 RCX: ffff888093ec6180
RDX: 0000000000000000 RSI: ffffc9000a017860 RDI: ffffc9000a017850
RBP: ffffc9000a017850 R08: dffffc0000000000 R09: ffffc9000a017850
R10: fffff52001402f0c R11: 0000000000000000 R12: ffffc9000a017860
R13: 0000000000008401 R14: ffffc9000a017850 R15: dffffc0000000000
FS:  00007f292d4ef700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fef820e7000 CR3: 00000000937fd000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400