diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2023-09-29 21:11:41 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2024-02-25 02:10:31 -0500 |
| commit | cdb67fdeed72248475b1c849699495ef290a1634 (patch) | |
| tree | e420dff77379ba8197a12b172b94320df2a81dcc /fs/namei.c | |
| parent | 583340de1d8b2d6a474eccd5e7d9f7f42f061e1b (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.c | 6 |
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); |