6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexander Sverdlin alexander.sverdlin@siemens.com
commit c14ecb555c3ee80eeb030a4e46d00e679537f03a upstream.
KCSAN reports:
BUG: KCSAN: data-race in do_raw_write_lock / do_raw_write_lock
write (marked) to 0xffff800009cf504c of 4 bytes by task 1102 on cpu 1: do_raw_write_lock+0x120/0x204 _raw_write_lock_irq do_exit call_usermodehelper_exec_async ret_from_fork
read to 0xffff800009cf504c of 4 bytes by task 1103 on cpu 0: do_raw_write_lock+0x88/0x204 _raw_write_lock_irq do_exit call_usermodehelper_exec_async ret_from_fork
value changed: 0xffffffff -> 0x00000001
Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 1103 Comm: kworker/u4:1 6.1.111
Commit 1a365e822372 ("locking/spinlock/debug: Fix various data races") has adressed most of these races, but seems to be not consistent/not complete.
From do_raw_write_lock() only debug_write_lock_after() part has been
converted to WRITE_ONCE(), but not debug_write_lock_before() part. Do it now.
Fixes: 1a365e822372 ("locking/spinlock/debug: Fix various data races") Reported-by: Adrian Freihofer adrian.freihofer@siemens.com Signed-off-by: Alexander Sverdlin alexander.sverdlin@siemens.com Signed-off-by: Boqun Feng boqun.feng@gmail.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Paul E. McKenney paulmck@kernel.org Acked-by: Waiman Long longman@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/locking/spinlock_debug.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/locking/spinlock_debug.c +++ b/kernel/locking/spinlock_debug.c @@ -183,8 +183,8 @@ void do_raw_read_unlock(rwlock_t *lock) static inline void debug_write_lock_before(rwlock_t *lock) { RWLOCK_BUG_ON(lock->magic != RWLOCK_MAGIC, lock, "bad magic"); - RWLOCK_BUG_ON(lock->owner == current, lock, "recursion"); - RWLOCK_BUG_ON(lock->owner_cpu == raw_smp_processor_id(), + RWLOCK_BUG_ON(READ_ONCE(lock->owner) == current, lock, "recursion"); + RWLOCK_BUG_ON(READ_ONCE(lock->owner_cpu) == raw_smp_processor_id(), lock, "cpu recursion"); }