Commit c7fd62bc69d02 ("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: c7fd62bc69d02 ("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+ --- drivers/hwtracing/stm/policy.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c index 4b9e44b227d8..4f932a419752 100644 --- a/drivers/hwtracing/stm/policy.c +++ b/drivers/hwtracing/stm/policy.c @@ -345,7 +345,11 @@ void stp_policy_unbind(struct stp_policy *policy) stm->policy = NULL; policy->stm = NULL;
+ /* + * Drop the reference on the protocol driver and lose the link. + */ stm_put_protocol(stm->pdrv); + stm->pdrv = NULL; stm_put_device(stm); }