From: Oleg Nesterov Date: Fri, 21 Aug 2015 17:42:55 +0000 (+0200) Subject: locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=95b19f684c61ffc9b039e02c5d1113c2d8cd7105;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe This is the temporary ugly hack which will be reverted later. We only need it to ensure that the next patch will not break "change sb_writers to use percpu_rw_semaphore" patches routed via the VFS tree. The alloc_super()->destroy_super() error path assumes that it is safe to call percpu_free_rwsem() after kzalloc() without percpu_init_rwsem(), so let's not disappoint it. Signed-off-by: Oleg Nesterov Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index e2621fbbcbd1..9529a30ec57b 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -26,6 +26,13 @@ EXPORT_SYMBOL_GPL(__percpu_init_rwsem); void percpu_free_rwsem(struct percpu_rw_semaphore *brw) { + /* + * XXX: temporary kludge. The error path in alloc_super() + * assumes that percpu_free_rwsem() is safe after kzalloc(). + */ + if (!brw->fast_read_ctr) + return; + free_percpu(brw->fast_read_ctr); brw->fast_read_ctr = NULL; /* catch use after free bugs */ }