From 94c0d4ecbe7f9fe56e052b26b2ab484e246c07b4 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 12 Jul 2011 21:40:23 -0400 Subject: Fix ->d_lock locking order in unlazy_walk() Make sure that child is still a child of parent before nested locking of child->d_lock in unlazy_walk(); otherwise we are risking a violation of locking order and deadlocks. Signed-off-by: Al Viro --- fs/namei.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 0223c41..5c867dd 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -433,6 +433,8 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) goto err_parent; BUG_ON(nd->inode != parent->d_inode); } else { + if (dentry->d_parent != parent) + goto err_parent; spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); if (!__d_rcu_to_refcount(dentry, nd->seq)) goto err_child; -- cgit v1.1 From 59430262401bec02d415179c43dbe5b8819c09ce Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 18 Jul 2011 15:43:29 -0700 Subject: vfs: fix race in rcu lookup of pruned dentry Don't update *inode in __follow_mount_rcu() until we'd verified that there is mountpoint there. Kudos to Hugh Dickins for catching that one in the first place and eventually figuring out the solution (and catching a braino in the earlier version of patch). Signed-off-by: Linus Torvalds Signed-off-by: Al Viro --- fs/namei.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 5c867dd..14ab8d3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -942,7 +942,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, * Don't forget we might have a non-mountpoint managed dentry * that wants to block transit. */ - *inode = path->dentry->d_inode; if (unlikely(managed_dentry_might_block(path->dentry))) return false; @@ -955,6 +954,12 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, path->mnt = mounted; path->dentry = mounted->mnt_root; nd->seq = read_seqcount_begin(&path->dentry->d_seq); + /* + * Update the inode too. We don't need to re-check the + * dentry sequence number here after this d_inode read, + * because a mount-point is always pinned. + */ + *inode = path->dentry->d_inode; } return true; } -- cgit v1.1