Avoid that closing /dev/infiniband/umad<n> or /dev/infiniband/issm<n>
triggers a use-after-free. __fput() invokes f_op->release() before it
invokes cdev_put(). Make sure that the ib_umad_device structure is
freed by the cdev_put() call instead of f_op->release(). This avoids
that changing the port mode from IB into Ethernet and back to IB
followed by restarting opensmd triggers the following kernel oops:
general protection fault: 0000 [#1] PREEMPT SMP
RIP: 0010:[<ffffffff810cc65c>] [<ffffffff810cc65c>] module_put+0x2c/0x170
Call Trace:
[<ffffffff81190f20>] cdev_put+0x20/0x30
[<ffffffff8118e2ce>] __fput+0x1ae/0x1f0
[<ffffffff8118e35e>] ____fput+0xe/0x10
[<ffffffff810723bc>] task_work_run+0xac/0xe0
[<ffffffff81002a9f>] do_notify_resume+0x9f/0xc0
[<ffffffff814b8398>] int_signal+0x12/0x17
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=75051
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>
Cc: <stable@vger.kernel.org> # 3.x: 8ec0a0e6b5: IB/umad: Fix error handling
Signed-off-by: Roland Dreier <roland@purestorage.com>
60e1751cb5