From 97242f99a013950af63effa0732f8ef7db4e31ec Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 1 Aug 2015 19:59:28 -0400 Subject: [PATCH] link_path_walk(): be careful when failing with ENOTDIR In RCU mode we might end up with dentry evicted just we check that it's a directory. In such case we should return ECHILD rather than ENOTDIR, so that pathwalk would be retries in non-RCU mode. Breakage had been introduced in commit b18825a - prior to that we were looking at nd->inode, which had been fetched before verifying that ->d_seq was still valid. That form of check would only be satisfied if at some point the pathname prefix would indeed have resolved to a non-directory. The fix consists of checking ->d_seq after we'd run into a non-directory dentry, and failing with ECHILD in case of mismatch. Note that all branches since 3.12 have that problem... Signed-off-by: Al Viro --- fs/namei.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index ae4e4c18b2ac..fbbcf0993312 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1954,8 +1954,13 @@ OK: continue; } } - if (unlikely(!d_can_lookup(nd->path.dentry))) + if (unlikely(!d_can_lookup(nd->path.dentry))) { + if (nd->flags & LOOKUP_RCU) { + if (unlazy_walk(nd, NULL, 0)) + return -ECHILD; + } return -ENOTDIR; + } } }