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linux/drivers/hwtracing/stm
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Alexander Shishkin 614662016d stm class: Lose the protocol driver when dropping its reference 
commit 0a8f72fafb upstream.

Commit c7fd62bc69 ("stm class: Introduce framing protocol drivers")
forgot to tear down the link between an stm device and its protocol
driver when policy is removed. This leads to an invalid pointer reference
if one tries to write to an stm device after the policy has been removed
and the protocol driver module unloaded, leading to the below splat:

> BUG: unable to handle page fault for address: ffffffffc0737068
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 3d780f067 P4D 3d780f067 PUD 3d7811067 PMD 492781067 PTE 0
> Oops: 0000 [#1] SMP NOPTI
> CPU: 1 PID: 26122 Comm: cat Not tainted 5.4.0-rc5+ #1
> RIP: 0010:stm_output_free+0x40/0xc0 [stm_core]
> Call Trace:
>  stm_char_release+0x3e/0x70 [stm_core]
>  __fput+0xc6/0x260
>  ____fput+0xe/0x10
>  task_work_run+0x9d/0xc0
>  exit_to_usermode_loop+0x103/0x110
>  do_syscall_64+0x19d/0x1e0
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix this by tearing down the link from an stm device to its protocol
driver when the policy involving that driver is removed.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Fixes: c7fd62bc69 ("stm class: Introduce framing protocol drivers")
Reported-by: Ammy Yi <ammy.yi@intel.com>
Tested-by: Ammy Yi <ammy.yi@intel.com>
CC: stable@vger.kernel.org # v4.20+
Link: https://lore.kernel.org/r/20191114064201.43089-2-alexander.shishkin@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2019-12-17 19:56:41 +01:00
..
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile stm class: Add MIPI SyS-T protocol support 2018-10-11 12:12:54 +02:00
console.c
…
core.c LED updates for 5.4-rc1 2019-09-17 18:40:42 -07:00
dummy_stm.c stm class: Make dummy's master/channel ranges configurable 2018-03-28 18:47:18 +03:00
ftrace.c coresight: Moving framework and drivers to SPDX identifier 2018-05-14 16:19:59 +02:00
heartbeat.c stm class: heartbeat: Fix whitespace 2018-10-11 12:12:55 +02:00
p_basic.c stm class: Factor out default framing protocol 2018-10-11 12:12:54 +02:00
p_sys-t.c stm class: p_sys-t: Add support for CLOCKSYNC packets 2018-10-11 12:12:54 +02:00
policy.c stm class: Lose the protocol driver when dropping its reference 2019-12-17 19:56:41 +01:00
stm.h stm class: Add a helper for writing data packets 2018-10-11 12:12:54 +02:00