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Date:   Fri, 07 May 2021 22:05:19 -0700
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Subject: [syzbot] WARNING: suspicious RCU usage in tomoyo_encode2
From:   syzbot <syzbot+dbea9c4c82135d4f5da3@syzkaller.appspotmail.com>
To:     jmorris@namei.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        penguin-kernel@I-love.SAKURA.ne.jp, serge@hallyn.com,
        syzkaller-bugs@googlegroups.com, takedakn@nttdata.co.jp
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Hello,

syzbot found the following issue on:

HEAD commit:    d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=152ab345d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe
dashboard link: https://syzkaller.appspot.com/bug?extid=dbea9c4c82135d4f5da3

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+dbea9c4c82135d4f5da3@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
5.12.0-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8304 Illegal context switch in RCU-bh read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
1 lock held by systemd-udevd/11603:
 #0: 
ffffffff8c712b18
 (
tomoyo_ss
){....}-{0:0}
, at: tomoyo_path_perm+0x1c1/0x400 security/tomoyo/file.c:847

stack backtrace:
CPU: 1 PID: 11603 Comm: systemd-udevd Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 ___might_sleep+0x229/0x2c0 kernel/sched/core.c:8304
 might_alloc include/linux/sched/mm.h:197 [inline]
 slab_pre_alloc_hook mm/slab.h:497 [inline]
 slab_alloc_node mm/slub.c:2827 [inline]
 slab_alloc mm/slub.c:2916 [inline]
 __kmalloc+0x26f/0x300 mm/slub.c:4054
 kmalloc include/linux/slab.h:561 [inline]
 kzalloc include/linux/slab.h:686 [inline]
 tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45
 tomoyo_encode2 security/tomoyo/realpath.c:31 [inline]
 tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822
 security_inode_getattr+0xcf/0x140 security/security.c:1295
 vfs_getattr fs/stat.c:131 [inline]
 vfs_statx+0x164/0x390 fs/stat.c:199
 vfs_fstatat fs/stat.c:217 [inline]
 vfs_stat include/linux/fs.h:3380 [inline]
 __do_sys_newstat+0x91/0x110 fs/stat.c:359
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7ffa23631295
Code: 00 00 00 e8 5d 01 00 00 48 83 c4 18 c3 0f 1f 84 00 00 00 00 00 83 ff 01 48 89 f0 77 30 48 89 c7 48 89 d6 b8 04 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 03 f3 c3 90 48 8b 15 d1 db 2b 00 f7 d8 64 89
RSP: 002b:00007fff554379b8 EFLAGS: 00000246
 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000558bf63356b0 RCX: 00007ffa23631295
RDX: 00007fff554379c0 RSI: 00007fff554379c0 RDI: 00007fff55437a70
RBP: 00007fff55437ae0 R08: 000000000000c0c0 R09: 0000000000000000
R10: 00007fff55437ac0 R11: 0000000000000246 R12: 00007fff55437af0
R13: 0000000000000001 R14: 0000558bf63353b0 R15: 000000000000000e


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