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authorAl Viro <viro@zeniv.linux.org.uk>2023-09-29 21:11:41 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2024-02-25 02:10:31 -0500
commitcdb67fdeed72248475b1c849699495ef290a1634 (patch)
treee420dff77379ba8197a12b172b94320df2a81dcc /fs/namei.c
parent583340de1d8b2d6a474eccd5e7d9f7f42f061e1b (diff)
rcu pathwalk: prevent bogus hard errors from may_lookup()
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. Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c6
1 files changed, 5 insertions, 1 deletions
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);