From a51cb91d81f8e6fc4e5e08b772cc3ceb13ac9d37 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 6 Jul 2011 12:33:55 +0200 Subject: [PATCH] fs: fix lock initialization locks_alloc_lock() assumed that the allocated struct file_lock is already initialized to zero members. This is only true for the first allocation of the structure, after reuse some of the members will have random values. This will for example result in passing random fl_start values to userspace in fuse for FL_FLOCK locks, which is an information leak at best. Fix by reinitializing those members which may be non-zero after freeing. Signed-off-by: Miklos Szeredi CC: stable@kernel.org Signed-off-by: Linus Torvalds --- fs/locks.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 0a4f50dfadfb..b286539d547a 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -160,10 +160,28 @@ EXPORT_SYMBOL_GPL(unlock_flocks); static struct kmem_cache *filelock_cache __read_mostly; +static void locks_init_lock_always(struct file_lock *fl) +{ + fl->fl_next = NULL; + fl->fl_fasync = NULL; + fl->fl_owner = NULL; + fl->fl_pid = 0; + fl->fl_nspid = NULL; + fl->fl_file = NULL; + fl->fl_flags = 0; + fl->fl_type = 0; + fl->fl_start = fl->fl_end = 0; +} + /* Allocate an empty lock structure. */ struct file_lock *locks_alloc_lock(void) { - return kmem_cache_alloc(filelock_cache, GFP_KERNEL); + struct file_lock *fl = kmem_cache_alloc(filelock_cache, GFP_KERNEL); + + if (fl) + locks_init_lock_always(fl); + + return fl; } EXPORT_SYMBOL_GPL(locks_alloc_lock); @@ -200,17 +218,9 @@ void locks_init_lock(struct file_lock *fl) INIT_LIST_HEAD(&fl->fl_link); INIT_LIST_HEAD(&fl->fl_block); init_waitqueue_head(&fl->fl_wait); - fl->fl_next = NULL; - fl->fl_fasync = NULL; - fl->fl_owner = NULL; - fl->fl_pid = 0; - fl->fl_nspid = NULL; - fl->fl_file = NULL; - fl->fl_flags = 0; - fl->fl_type = 0; - fl->fl_start = fl->fl_end = 0; fl->fl_ops = NULL; fl->fl_lmops = NULL; + locks_init_lock_always(fl); } EXPORT_SYMBOL(locks_init_lock); -- 2.20.1