NFSv4: Handle case where the lookup of a directory fails

Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit?id=ce8c552b88ca25d775ecd0a0fbef4e0e03de9ed2
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2022-24448

commit ac795161c93699d600db16c1a8cc23a65a1eceaf upstream.

If the application sets the O_DIRECTORY flag, and tries to open a
regular file, nfs_atomic_open() will punt to doing a regular lookup.
If the server then returns a regular file, we will happily return a
file descriptor with uninitialised open state.

The fix is to return the expected ENOTDIR error in these cases.

Reported-by: Lyu Tao <tao.lyu@epfl.ch>
Fixes: 0dd2b474d0b6 ("nfs: implement i_op->atomic_open()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name NFSv4-Handle-case-where-the-lookup-of-a-directory-fa.patch

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 8b963c72dd3b1aab88569d918144f6a4b3b267ad..6e55d9763a1981f3abcaa083b955f9985b79ac0a 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1777,6 +1777,19 @@ out:
 
 no_open:
        res = nfs_lookup(dir, dentry, lookup_flags);
+       if (!res) {
+               inode = d_inode(dentry);
+               if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
+                   !S_ISDIR(inode->i_mode))
+                       res = ERR_PTR(-ENOTDIR);
+       } else if (!IS_ERR(res)) {
+               inode = d_inode(res);
+               if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
+                   !S_ISDIR(inode->i_mode)) {
+                       dput(res);
+                       res = ERR_PTR(-ENOTDIR);
+               }
+       }
        if (switched) {
                d_lookup_done(dentry);
                if (!res)