This is a note to let you know that I've just added the patch titled RCU pathwalk breakage when running into a symlink overmounting something to the 4.0-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: rcu-pathwalk-breakage-when-running-into-a-symlink-overmounting-something.patch and it can be found in the queue-4.0 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 Mon Sep 17 00:00:00 2001 From: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Date: Fri, 24 Apr 2015 15:47:07 -0400 Subject: RCU pathwalk breakage when running into a symlink overmounting something From: Al Viro <viro@xxxxxxxxxxxxxxxxxx> commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 upstream. Calling unlazy_walk() in walk_component() and do_last() when we find a symlink that needs to be followed doesn't acquire a reference to vfsmount. That's fine when the symlink is on the same vfsmount as the parent directory (which is almost always the case), but it's not always true - one _can_ manage to bind a symlink on top of something. And in such cases we end up with excessive mntput(). Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/namei.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/namei.c +++ b/fs/namei.c @@ -1591,7 +1591,8 @@ static inline int walk_component(struct if (should_follow_link(path->dentry, follow)) { if (nd->flags & LOOKUP_RCU) { - if (unlikely(unlazy_walk(nd, path->dentry))) { + if (unlikely(nd->path.mnt != path->mnt || + unlazy_walk(nd, path->dentry))) { err = -ECHILD; goto out_err; } @@ -3047,7 +3048,8 @@ finish_lookup: if (should_follow_link(path->dentry, !symlink_ok)) { if (nd->flags & LOOKUP_RCU) { - if (unlikely(unlazy_walk(nd, path->dentry))) { + if (unlikely(nd->path.mnt != path->mnt || + unlazy_walk(nd, path->dentry))) { error = -ECHILD; goto out; } Patches currently in stable-queue which might be from viro@xxxxxxxxxxxxxxxxxx are queue-4.0/fs-binfmt_elf.c-fix-bug-in-loading-of-pie-binaries.patch queue-4.0/rcu-pathwalk-breakage-when-running-into-a-symlink-overmounting-something.patch queue-4.0/nfs-fix-bug-crash-in-notify_change-with-patch-to-chown_common.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html