general protection fault in jffs2_parse_param

[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=12acb307900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b12e84189082991c
dashboard link: https://syzkaller.appspot.com/bug?extid=9765367bb86a19d38732
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=175909d9900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=179b3cc3900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9765367bb86a19d38732 at syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 1 PID: 6866 Comm: syz-executor202 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:jffs2_parse_param+0x141/0x330 fs/jffs2/super.c:206
Code: 48 c1 ea 03 4d 63 fc 80 3c 02 00 0f 85 de 01 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 75 00 49 8d 7e 08 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 c8 01 00 00 4d 8b 76 08 4c 89 ff 4c 89 f6 e8 d6
RSP: 0018:ffffc90001087b78 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8880932c9c00 RCX: ffffffff82882084
RDX: 0000000000000001 RSI: ffffffff82882096 RDI: 0000000000000008
RBP: 1ffff92000210f6f R08: 0000000000000001 R09: 0000000000000003
R10: 00000000003fffff R11: 0000000000000000 R12: 0000000000000000
R13: ffff88808de2a000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000002198880(0000) GS:ffff8880ae500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043e830 CR3: 00000000a11a3000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vfs_parse_fs_param fs/fs_context.c:117 [inline]
 vfs_parse_fs_param+0x203/0x550 fs/fs_context.c:98
 vfs_parse_fs_string+0xe6/0x150 fs/fs_context.c:161
 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:201
 do_new_mount fs/namespace.c:2871 [inline]
 path_mount+0x133f/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: 0033:0x44699a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d ae 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 ae fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffc381bf788 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc381bf7d0 RCX: 000000000044699a
RDX: 0000000020001300 RSI: 0000000020001340 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007ffc381bf7d0 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401c80
R13: 0000000000401d10 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 9cf0f624124bffcb ]---
RIP: 0010:jffs2_parse_param+0x141/0x330 fs/jffs2/super.c:206
Code: 48 c1 ea 03 4d 63 fc 80 3c 02 00 0f 85 de 01 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 75 00 49 8d 7e 08 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 c8 01 00 00 4d 8b 76 08 4c 89 ff 4c 89 f6 e8 d6
RSP: 0018:ffffc90001087b78 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8880932c9c00 RCX: ffffffff82882084
RDX: 0000000000000001 RSI: ffffffff82882096 RDI: 0000000000000008
RBP: 1ffff92000210f6f R08: 0000000000000001 R09: 0000000000000003
R10: 00000000003fffff R11: 0000000000000000 R12: 0000000000000000
R13: ffff88808de2a000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000002198880(0000) GS:ffff8880ae500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043e830 CR3: 00000000a11a3000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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