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syzbot reports a crash with tty polling, which is using the double poll handling: general protection fault, probably for non-canonical address 0xdffffc0000000009: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f] CPU: 0 PID: 6874 Comm: syz-executor749 Not tainted 5.9.0-rc6-next-20200924-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:io_poll_get_single fs/io_uring.c:4778 [inline] RIP: 0010:io_poll_double_wake+0x51/0x510 fs/io_uring.c:4845 Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 9e 03 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 48 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 06 0f 8e 63 03 00 00 0f b6 6b 48 bf 06 00 00 RSP: 0018:ffffc90001c1fb70 EFLAGS: 00010006 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000004 RDX: 0000000000000009 RSI: ffffffff81d9b3ad RDI: 0000000000000048 RBP: dffffc0000000000 R08: ffff8880a3cac798 R09: ffffc90001c1fc60 R10: fffff52000383f73 R11: 0000000000000000 R12: 0000000000000004 R13: ffff8880a3cac798 R14: ffff8880a3cac7a0 R15: 0000000000000004 FS: 0000000001f98880(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f18886916c0 CR3: 0000000094c5a000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __wake_up_common+0x147/0x650 kernel/sched/wait.c:93 __wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:123 tty_ldisc_hangup+0x1cf/0x680 drivers/tty/tty_ldisc.c:735 __tty_hangup.part.0+0x403/0x870 drivers/tty/tty_io.c:625 __tty_hangup drivers/tty/tty_io.c:575 [inline] tty_vhangup+0x1d/0x30 drivers/tty/tty_io.c:698 pty_close+0x3f5/0x550 drivers/tty/pty.c:79 tty_release+0x455/0xf60 drivers/tty/tty_io.c:1679 __fput+0x285/0x920 fs/file_table.c:281 task_work_run+0xdd/0x190 kernel/task_work.c:141 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop kernel/entry/common.c:165 [inline] exit_to_user_mode_prepare+0x1e2/0x1f0 kernel/entry/common.c:192 syscall_exit_to_user_mode+0x7a/0x2c0 kernel/entry/common.c:267 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x401210 which is due to a failure in removing the double poll wait entry if we hit a wakeup match. This can cause multiple invocations of the wakeup, which isn't safe. Cc: stable@vger.kernel.org # v5.8 Reported-by: syzbot+81b3883093f772addf6d@syzkaller.appspotmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.