From 4f73c7d342d57d065bdbc0995cb56d8d1701b0c0 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 30 Apr 2014 09:31:47 -0400 Subject: cifs: fix potential races in cifs_revalidate_mapping The handling of the CIFS_INO_INVALID_MAPPING flag is racy. It's possible for two tasks to attempt to revalidate the mapping at the same time. The first sees that CIFS_INO_INVALID_MAPPING is set. It clears the flag and then calls invalidate_inode_pages2 to start shooting down the pagecache. While that's going on, another task checks the flag and sees that it's clear. It then ends up trusting the pagecache to satisfy a read when it shouldn't. Fix this by adding a bitlock to ensure that the clearing of the flag is atomic with respect to the actual cache invalidation. Also, move the other existing users of cifs_invalidate_mapping to use a new cifs_zap_mapping() function that just sets the INVALID_MAPPING bit and then uses the standard codepath to handle the invalidation. Signed-off-by: Jeff Layton Signed-off-by: Steve French --- fs/cifs/cifsglob.h | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/cifs/cifsglob.h') diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 69da55b750e7..630e0f4b2c66 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1118,6 +1118,7 @@ struct cifsInodeInfo { #define CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2 (2) /* Downgrade oplock to L2 */ #define CIFS_INO_DELETE_PENDING (3) /* delete pending on server */ #define CIFS_INO_INVALID_MAPPING (4) /* pagecache is invalid */ +#define CIFS_INO_LOCK (5) /* lock bit for synchronization */ unsigned long flags; spinlock_t writers_lock; unsigned int writers; /* Number of writers on this inode */ -- cgit v1.2.1