If lazy call of ->permission() returns a hard error, check that
try_to_unlazy() succeeds before returning it. That both makes
life easier for ->permission() instances and closes the race
in ENOTDIR handling - it is possible that positive d_can_lookup()
seen in link_path_walk() applies to the state *after* unlink() +
mkdir(), while nd->inode matches the state prior to that.
Normally seeing e.g. EACCES from permission check in rcu pathwalk
means that with some timings non-rcu pathwalk would've run into
the same; however, running into a non-executable regular file
in the middle of a pathname would not get to permission check -
it would fail with ENOTDIR instead.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/namei.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/namei.c b/fs/namei.c
index 4e0de939fea1..9342fa6a38c2 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1717,7 +1717,11 @@ static inline int may_lookup(struct mnt_idmap *idmap,
{
if (nd->flags & LOOKUP_RCU) {
int err = inode_permission(idmap, nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
- if (err != -ECHILD || !try_to_unlazy(nd))
+ if (!err) // success, keep going
+ return 0;
+ if (!try_to_unlazy(nd))
+ return -ECHILD; // redo it all non-lazy
+ if (err != -ECHILD) // hard error
return err;
}
return inode_permission(idmap, nd->inode, MAY_EXEC);
--
2.39.2
