Subject: INFO: task can't die in p9_client_rpc

From: syzbot <[email-masked]>
Date: Sun, 02 Aug 2020 12:59:25 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    01830e6c Add linux-next specific files for 20200731
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=176146cc900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2e226b2d1364112c
dashboard link: https://syzkaller.appspot.com/bug?extid=a42aa715d3d32226792a
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: [email-masked]

INFO: task syz-executor.5:24879 can't die for more than 143 seconds.
syz-executor.5  D25688 24879   7480 0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3669 [inline]
 __schedule+0x8e5/0x21e0 kernel/sched/core.c:4418
 schedule+0xd0/0x2a0 kernel/sched/core.c:4493
 p9_client_rpc+0x3b5/0x11f0 net/9p/client.c:757
 p9_client_flush+0x1f9/0x430 net/9p/client.c:665
 p9_client_rpc+0xf93/0x11f0 net/9p/client.c:782
 p9_client_version net/9p/client.c:953 [inline]
 p9_client_create+0xa8f/0x10c0 net/9p/client.c:1053
 v9fs_session_init+0x1dd/0x1770 fs/9p/v9fs.c:406
 v9fs_mount+0x79/0x970 fs/9p/vfs_super.c:124
 legacy_get_tree+0x105/0x220 fs/fs_context.c:592
 vfs_get_tree+0x89/0x2f0 fs/super.c:1549
 do_new_mount fs/namespace.c:2912 [inline]
 do_mount+0x14f6/0x1e20 fs/namespace.c:3238
 __do_sys_mount fs/namespace.c:3448 [inline]
 __se_sys_mount fs/namespace.c:3425 [inline]
 __x64_sys_mount+0x18f/0x230 fs/namespace.c:3425
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cc79
Code: Bad RIP value.
RSP: 002b:00007f92f26b9c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000020480 RCX: 000000000045cc79
RDX: 0000000020000100 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 000000000078bf50 R08: 0000000020000200 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007fff9a822f9f R14: 00007f92f26ba9c0 R15: 000000000078bf0c

Showing all locks held in the system:
1 lock held by khungtaskd/1164:
 #0: ffffffff89c52a80 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5823
1 lock held by in:imklog/6729:
 #0: ffff8880a97c7db0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:930

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