From 3abb17e82f08628b59e20d8cbcb55e2204180f69 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 16 Feb 2011 08:56:55 -0800 Subject: vfs: fix BUG_ON() in fs/namei.c:1461 When Al moved the nameidata_dentry_drop_rcu_maybe() call into the do_follow_link function in commit 844a391799c2 ("nothing in do_follow_link() is going to see RCU"), he mistakenly left the BUG_ON(inode != path->dentry->d_inode); behind. Which would otherwise be ok, but that BUG_ON() really needs to be _after_ dropping RCU, since the dentry isn't necessarily stable otherwise. So complete the code movement in that commit, and move the BUG_ON() into do_follow_link() too. This means that we need to pass in 'inode' as an argument (just for this one use), but that's a small thing. And eventually we may be confident enough in our path lookup that we can just remove the BUG_ON() and the unnecessary inode argument. Reported-and-tested-by: Eric Dumazet Acked-by: Al Viro Signed-off-by: Linus Torvalds --- fs/namei.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 9e701e28a329..0087cf9c2c6b 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -795,7 +795,7 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p) * Without that kind of total limit, nasty chains of consecutive * symlinks can cause almost arbitrarily long lookups. */ -static inline int do_follow_link(struct path *path, struct nameidata *nd) +static inline int do_follow_link(struct inode *inode, struct path *path, struct nameidata *nd) { void *cookie; int err = -ELOOP; @@ -803,6 +803,7 @@ static inline int do_follow_link(struct path *path, struct nameidata *nd) /* We drop rcu-walk here */ if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry)) return -ECHILD; + BUG_ON(inode != path->dentry->d_inode); if (current->link_count >= MAX_NESTED_LINKS) goto loop; @@ -1413,8 +1414,7 @@ exec_again: goto out_dput; if (inode->i_op->follow_link) { - BUG_ON(inode != next.dentry->d_inode); - err = do_follow_link(&next, nd); + err = do_follow_link(inode, &next, nd); if (err) goto return_err; nd->inode = nd->path.dentry->d_inode; @@ -1458,8 +1458,7 @@ last_component: break; if (inode && unlikely(inode->i_op->follow_link) && (lookup_flags & LOOKUP_FOLLOW)) { - BUG_ON(inode != next.dentry->d_inode); - err = do_follow_link(&next, nd); + err = do_follow_link(inode, &next, nd); if (err) goto return_err; nd->inode = nd->path.dentry->d_inode; -- cgit v1.2.3