Commits
Xiubo Li committed b34e9a15b37
uio: fix possible circular locking dependency
The call trace:
XXX/1910 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff97008c87>] might_fault+0x57/0xb0
but task is already holding lock:
(&idev->info_lock){+.+...}, at: [<ffffffffc0638a06>] uio_write+0x46/0x130 [uio]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&idev->info_lock){+.+...}:
[<ffffffff96f31fc9>] lock_acquire+0x99/0x1e0
[<ffffffff975edad3>] mutex_lock_nested+0x93/0x410
[<ffffffffc063873d>] uio_mmap+0x2d/0x170 [uio]
[<ffffffff97016b58>] mmap_region+0x428/0x650
[<ffffffff97017138>] do_mmap+0x3b8/0x4e0
[<ffffffff96ffaba3>] vm_mmap_pgoff+0xd3/0x120
[<ffffffff97015261>] SyS_mmap_pgoff+0x1f1/0x270
[<ffffffff96e387c2>] SyS_mmap+0x22/0x30
[<ffffffff975ff315>] system_call_fastpath+0x1c/0x21
-> #0 (&mm->mmap_sem){++++++}:
[<ffffffff96f30e9c>] __lock_acquire+0xdac/0x15f0
[<ffffffff96f31fc9>] lock_acquire+0x99/0x1e0
[<ffffffff97008cb4>] might_fault+0x84/0xb0
[<ffffffffc0638a74>] uio_write+0xb4/0x130 [uio]
[<ffffffff9706ffa3>] vfs_write+0xc3/0x1f0
[<ffffffff97070e2a>] SyS_write+0x8a/0x100
[<ffffffff975ff315>] system_call_fastpath+0x1c/0x21
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&idev->info_lock);
lock(&mm->mmap_sem);
lock(&idev->info_lock);
lock(&mm->mmap_sem);
*** DEADLOCK ***
1 lock held by XXX/1910:
#0: (&idev->info_lock){+.+...}, at: [<ffffffffc0638a06>] uio_write+0x46/0x130 [uio]
stack backtrace:
CPU: 0 PID: 1910 Comm: XXX Kdump: loaded Not tainted #1
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017
Call Trace:
[<ffffffff975e9211>] dump_stack+0x19/0x1b
[<ffffffff975e260a>] print_circular_bug+0x1f9/0x207
[<ffffffff96f2f6a7>] check_prevs_add+0x957/0x960
[<ffffffff96f30e9c>] __lock_acquire+0xdac/0x15f0
[<ffffffff96f2fb19>] ? mark_held_locks+0xb9/0x140
[<ffffffff96f31fc9>] lock_acquire+0x99/0x1e0
[<ffffffff97008c87>] ? might_fault+0x57/0xb0
[<ffffffff97008cb4>] might_fault+0x84/0xb0
[<ffffffff97008c87>] ? might_fault+0x57/0xb0
[<ffffffffc0638a74>] uio_write+0xb4/0x130 [uio]
[<ffffffff9706ffa3>] vfs_write+0xc3/0x1f0
[<ffffffff9709349c>] ? fget_light+0xfc/0x510
[<ffffffff97070e2a>] SyS_write+0x8a/0x100
[<ffffffff975ff315>] system_call_fastpath+0x1c/0x21
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>