From 6d4b9e38d3980826abccfbd90e95bf4bd41b8dd2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 26 Dec 2011 10:25:26 -0800 Subject: [PATCH] vfs: fix handling of lock allocation failure in lease-break case Bruce Fields notes that commit 778fc546f749 ("locks: fix tracking of inprogress lease breaks") introduced a possible error pointer dereference on failure to allocate memory. locks_conflict() will dereference the passed-in new lease lock structure that may be an error pointer. This means an open (without O_NONBLOCK set) on a file with a lease applied (generally only done when Samba or nfsd (with v4) is running) could crash if a kmalloc() fails. So instead of playing games with IS_ERROR() all over the place, just check the allocation failure early. That makes the code more straightforward, and avoids this possible bad pointer dereference. Based-on-patch-by: J. Bruce Fields Cc: Al Viro Signed-off-by: Linus Torvalds --- fs/locks.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 3b0d05dcd7c1..637694bf3a03 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1205,6 +1205,8 @@ int __break_lease(struct inode *inode, unsigned int mode) int want_write = (mode & O_ACCMODE) != O_RDONLY; new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK); + if (IS_ERR(new_fl)) + return PTR_ERR(new_fl); lock_flocks(); @@ -1221,12 +1223,6 @@ int __break_lease(struct inode *inode, unsigned int mode) if (fl->fl_owner == current->files) i_have_this_lease = 1; - if (IS_ERR(new_fl) && !i_have_this_lease - && ((mode & O_NONBLOCK) == 0)) { - error = PTR_ERR(new_fl); - goto out; - } - break_time = 0; if (lease_break_time > 0) { break_time = jiffies + lease_break_time * HZ; @@ -1284,8 +1280,7 @@ restart: out: unlock_flocks(); - if (!IS_ERR(new_fl)) - locks_free_lock(new_fl); + locks_free_lock(new_fl); return error; } -- 2.39.2