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staging: vc04_services: Fix RCU dereference check

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In service_callback path RCU dereferenced pointer struct vchiq_service
need to be accessed inside rcu read-critical section.

Also userdata/user_service part of vchiq_service is accessed around
different synchronization mechanism, getting an extra reference to a
pointer keeps sematics simpler and avoids prolonged graceperiod.

Accessing vchiq_service with rcu_read_[lock/unlock] fixes below issue.

[   32.201659] =============================
[   32.201664] WARNING: suspicious RCU usage
[   32.201670] 5.15.11-rt24-v8+ #3 Not tainted
[   32.201680] -----------------------------
[   32.201685] drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h:529 suspicious rcu_dereference_check() usage!
[   32.201695]
[   32.201695] other info that might help us debug this:
[   32.201695]
[   32.201700]
[   32.201700] rcu_scheduler_active = 2, debug_locks = 1
[   32.201708] no locks held by vchiq-slot/0/98.
[   32.201715]
[   32.201715] stack backtrace:
[   32.201723] CPU: 1 PID: 98 Comm: vchiq-slot/0 Not tainted 5.15.11-rt24-v8+ #3
[   32.201733] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT)
[   32.201739] Call trace:
[   32.201742]  dump_backtrace+0x0/0x1b8
[   32.201772]  show_stack+0x20/0x30
[   32.201784]  dump_stack_lvl+0x8c/0xb8
[   32.201799]  dump_stack+0x18/0x34
[   32.201808]  lockdep_rcu_suspicious+0xe4/0xf8
[   32.201817]  service_callback+0x124/0x400
[   32.201830]  slot_handler_func+0xf60/0x1e20
[   32.201839]  kthread+0x19c/0x1a8
[   32.201849]  ret_from_fork+0x10/0x20

Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
Link: https://lore.kernel.org/r/20211231195406.5479-1-treasure4paddy@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Padmanabha Srinivasaiah 2021-12-31 20:54:03 +01:00 committed by Greg Kroah-Hartman
parent e783362eb5
commit 0cea730cac
1 changed files with 18 additions and 2 deletions
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20
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
View File

@ -1058,15 +1058,27 @@ service_callback(enum vchiq_reason reason, struct vchiq_header *header,
DEBUG_TRACE(SERVICE_CALLBACK_LINE);
rcu_read_lock();
service = handle_to_service(handle);
if (WARN_ON(!service))
if (WARN_ON(!service)) {
rcu_read_unlock();
return VCHIQ_SUCCESS;
}
user_service = (struct user_service *)service->base.userdata;
instance = user_service->instance;
if (!instance || instance->closing)
if (!instance || instance->closing) {
rcu_read_unlock();
return VCHIQ_SUCCESS;
}
/*
* As hopping around different synchronization mechanism,
* taking an extra reference results in simpler implementation.
*/
vchiq_service_get(service);
rcu_read_unlock();
vchiq_log_trace(vchiq_arm_log_level,
"%s - service %lx(%d,%p), reason %d, header %lx, instance %lx, bulk_userdata %lx",
@ -1097,6 +1109,7 @@ service_callback(enum vchiq_reason reason, struct vchiq_header *header,
bulk_userdata);
if (status != VCHIQ_SUCCESS) {
DEBUG_TRACE(SERVICE_CALLBACK_LINE);
vchiq_service_put(service);
return status;
}
}
@ -1105,10 +1118,12 @@ service_callback(enum vchiq_reason reason, struct vchiq_header *header,
if (wait_for_completion_interruptible(&user_service->remove_event)) {
vchiq_log_info(vchiq_arm_log_level, "%s interrupted", __func__);
DEBUG_TRACE(SERVICE_CALLBACK_LINE);
vchiq_service_put(service);
return VCHIQ_RETRY;
} else if (instance->closing) {
vchiq_log_info(vchiq_arm_log_level, "%s closing", __func__);
DEBUG_TRACE(SERVICE_CALLBACK_LINE);
vchiq_service_put(service);
return VCHIQ_ERROR;
}
DEBUG_TRACE(SERVICE_CALLBACK_LINE);
@ -1137,6 +1152,7 @@ service_callback(enum vchiq_reason reason, struct vchiq_header *header,
header = NULL;
}
DEBUG_TRACE(SERVICE_CALLBACK_LINE);
vchiq_service_put(service);
if (skip_completion)
return VCHIQ_SUCCESS;