general protection fault in reiserfs_security_init

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    325d0eab Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1671c0e3900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b12e84189082991c
dashboard link: https://syzkaller.appspot.com/bug?extid=690cb1e51970435f9775
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15705a3d900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=117b3281900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+690cb1e51970435f9775@xxxxxxxxxxxxxxxxxxxxxxxxx

REISERFS (device loop0): journal params: device loop0, size 15748, journal first block 18, max trans len 256, max batch 225, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using tea hash to sort names
REISERFS (device loop0): using 3.5.x disk format
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: 6874 Comm: syz-executor834 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:d_really_is_negative include/linux/dcache.h:472 [inline]
RIP: 0010:reiserfs_xattr_jcreate_nblocks fs/reiserfs/xattr.h:78 [inline]
RIP: 0010:reiserfs_security_init+0x285/0x4d0 fs/reiserfs/xattr_security.c:70
Code: 48 c1 ea 03 80 3c 02 00 0f 85 2b 02 00 00 4d 8b ad a0 05 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7d 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 23 02 00 00 49 83 7d 68 00 0f 84 62 01 00 00 48
RSP: 0018:ffffc90005827980 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000036 RCX: 000000000000006c
RDX: 000000000000000d RSI: ffffffff82009dd3 RDI: 0000000000000068
RBP: ffff88807d8441d0 R08: ffffc90005827a10 R09: ffffc90005827a18
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000005fa
R13: 0000000000000000 R14: ffff888094e60000 R15: 0000000000000000
FS:  0000000001036880(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5a6fb90ab4 CR3: 000000009a1ab000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 reiserfs_mkdir+0x2c9/0x980 fs/reiserfs/namei.c:821
 create_privroot fs/reiserfs/xattr.c:882 [inline]
 reiserfs_xattr_init+0x4de/0xb52 fs/reiserfs/xattr.c:1004
 reiserfs_fill_super+0x215d/0x2df3 fs/reiserfs/super.c:2177
 mount_bdev+0x32e/0x3f0 fs/super.c:1417
 legacy_get_tree+0x105/0x220 fs/fs_context.c:592
 vfs_get_tree+0x89/0x2f0 fs/super.c:1547
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x1387/0x20a0 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: 0033:0x447d9a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d a3 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 5a a3 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fffe558f5c8 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffe558f620 RCX: 0000000000447d9a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fffe558f5e0
RBP: 00007fffe558f5e0 R08: 00007fffe558f620 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000006
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003
Modules linked in:
---[ end trace e6a0a9f4ee2cea86 ]---
RIP: 0010:d_really_is_negative include/linux/dcache.h:472 [inline]
RIP: 0010:reiserfs_xattr_jcreate_nblocks fs/reiserfs/xattr.h:78 [inline]
RIP: 0010:reiserfs_security_init+0x285/0x4d0 fs/reiserfs/xattr_security.c:70
Code: 48 c1 ea 03 80 3c 02 00 0f 85 2b 02 00 00 4d 8b ad a0 05 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7d 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 23 02 00 00 49 83 7d 68 00 0f 84 62 01 00 00 48
RSP: 0018:ffffc90005827980 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000036 RCX: 000000000000006c
RDX: 000000000000000d RSI: ffffffff82009dd3 RDI: 0000000000000068
RBP: ffff88807d8441d0 R08: ffffc90005827a10 R09: ffffc90005827a18
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000005fa
R13: 0000000000000000 R14: ffff888094e60000 R15: 0000000000000000
FS:  0000000001036880(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff7d575b000 CR3: 000000009a1ab000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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