On Fri, 2020-10-16 at 01:12 -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: b2926c10 Add linux-next specific files for 20201016 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=12fc877f900000 > kernel config: https://syzkaller.appspot.com/x/.config?x=6160209582f55fb1 > dashboard link: https://syzkaller.appspot.com/bug?extid=4596e1fcf98efa7d1745 > compiler: gcc (GCC) 10.1.0-syz 20200507 > > 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+4596e1fcf98efa7d1745@xxxxxxxxxxxxxxxxxxxxxxxxx > > ============================= > WARNING: suspicious RCU usage > 5.9.0-next-20201016-syzkaller #0 Not tainted > ----------------------------- > include/linux/cgroup.h:494 suspicious rcu_dereference_check() usage! Introduced by the linux-next commits: 07950f53f85b ("io_uring: COW io_identity on mismatch") Can't find the patchset was posted anywhere. Anyway, this should fix it? --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1049,7 +1049,9 @@ static void io_init_identity(struct io_identity *id) id->files = current->files; id->mm = current->mm; #ifdef CONFIG_BLK_CGROUP + rcu_read_lock(); id->blkcg_css = blkcg_css(); + rcu_read_unlock(); #endif id->creds = current_cred(); id->nsproxy = current->nsproxy; > > other info that might help us debug this: > > > rcu_scheduler_active = 2, debug_locks = 1 > no locks held by syz-executor.0/8301. > > stack backtrace: > CPU: 0 PID: 8301 Comm: syz-executor.0 Not tainted 5.9.0-next-20201016- > syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google > 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x198/0x1fb lib/dump_stack.c:118 > task_css include/linux/cgroup.h:494 [inline] > blkcg_css include/linux/blk-cgroup.h:224 [inline] > blkcg_css include/linux/blk-cgroup.h:217 [inline] > io_init_identity+0x3a9/0x450 fs/io_uring.c:1052 > io_uring_alloc_task_context+0x176/0x250 fs/io_uring.c:7730 > io_uring_add_task_file+0x10d/0x180 fs/io_uring.c:8653 > io_uring_get_fd fs/io_uring.c:9144 [inline] > io_uring_create fs/io_uring.c:9308 [inline] > io_uring_setup+0x2727/0x3660 fs/io_uring.c:9342 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > RIP: 0033:0x45de59 > Code: 0d 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f7e11fe1bf8 EFLAGS: 00000206 ORIG_RAX: 00000000000001a9 > RAX: ffffffffffffffda RBX: 0000000020000080 RCX: 000000000045de59 > RDX: 00000000206d4000 RSI: 0000000020000080 RDI: 0000000000000087 > RBP: 000000000118c020 R08: 0000000020000040 R09: 0000000020000040 > R10: 0000000020000000 R11: 0000000000000206 R12: 00000000206d4000 > R13: 0000000020ee7000 R14: 0000000020000040 R15: 0000000020000000 > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
