Re: [syzbot] [gfs2?] WARNING: suspicious RCU usage in gfs2_permission

[syzbot <syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    2dac75696c6d Add linux-next specific files for 20231018
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13af5fe5680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6f8545e1ef7a2b66
dashboard link: https://syzkaller.appspot.com/bug?extid=3e5130844b0c0e2b4948
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=101c8d09680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11a07475680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2375f16ed327/disk-2dac7569.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c80aee6e2e6c/vmlinux-2dac7569.xz
kernel image: https://storage.googleapis.com/syzbot-assets/664dc23b738d/bzImage-2dac7569.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/5ce278ef6f36/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com

gfs2: fsid=syz:syz.0: first mount done, others may mount
=============================
WARNING: suspicious RCU usage
6.6.0-rc6-next-20231018-syzkaller #0 Not tainted
-----------------------------
fs/gfs2/inode.c:1877 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
no locks held by syz-executor120/5052.

stack backtrace:
CPU: 1 PID: 5052 Comm: syz-executor120 Not tainted 6.6.0-rc6-next-20231018-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
 lockdep_rcu_suspicious+0x20c/0x3b0 kernel/locking/lockdep.c:6711
 gfs2_permission+0x3f9/0x4c0 fs/gfs2/inode.c:1877
 do_inode_permission fs/namei.c:462 [inline]
 inode_permission fs/namei.c:529 [inline]
 inode_permission+0x384/0x5e0 fs/namei.c:504
 may_open+0x11c/0x400 fs/namei.c:3249
 do_open fs/namei.c:3619 [inline]
 path_openat+0x17aa/0x2ce0 fs/namei.c:3778
 do_filp_open+0x1de/0x430 fs/namei.c:3808
 do_sys_openat2+0x176/0x1e0 fs/open.c:1440
 do_sys_open fs/open.c:1455 [inline]
 __do_sys_openat fs/open.c:1471 [inline]
 __se_sys_openat fs/open.c:1466 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1466
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f5b23a31a11
Code: 75 57 89 f0 25 00 00 41 00 3d 00 00 41 00 74 49 80 3d 7a 06 0b 00 00 74 6d 89 da 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 93 00 00 00 48 8b 54 24 28 64 48 2b 14 25
RSP: 002b:00007ffe9ecd33a0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000010000 RCX: 00007f5b23a31a11
RDX: 0000000000010000 RSI: 0000000020037f80 RDI: 00000000ffffff9c
RBP: 0000000020037f80 R08: 00007ffe9ecd3470 R09: 0000000000037f13
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffe9ecd3470 R14: 0000000000000003 R15: 0000000001000000
 </TASK>


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