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SubjectRe: [PATCH] fs: fix lock initialization
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On Wed, Jul 06, 2011 at 12:33:55PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@suse.cz>
>
> 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.

Could you also just get rid of init_once() while you're at it?

--b.

>
> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
> CC: stable@kernel.org
> ---
> fs/locks.c | 30 ++++++++++++++++++++----------
> 1 file changed, 20 insertions(+), 10 deletions(-)
>
> Index: linux-2.6/fs/locks.c
> ===================================================================
> --- linux-2.6.orig/fs/locks.c 2011-07-04 17:06:01.000000000 +0200
> +++ linux-2.6/fs/locks.c 2011-07-04 17:06:04.000000000 +0200
> @@ -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 *f
> 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);
> --
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