This is a note to let you know that I've just added the patch titled
cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cifs-fix-dfs-traversal-oops-without-config_cifs_dfs_upcall.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 179a88a8558bbf42991d361595281f3e45d7edfc Mon Sep 17 00:00:00 2001
From: David Disseldorp <ddiss@xxxxxxx>
Date: Wed, 29 Mar 2023 22:24:06 +0200
Subject: cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL
From: David Disseldorp <ddiss@xxxxxxx>
commit 179a88a8558bbf42991d361595281f3e45d7edfc upstream.
When compiled with CONFIG_CIFS_DFS_UPCALL disabled, cifs_dfs_d_automount
is NULL. cifs.ko logic for mapping CIFS_FATTR_DFS_REFERRAL attributes to
S_AUTOMOUNT and corresponding dentry flags is retained regardless of
CONFIG_CIFS_DFS_UPCALL, leading to a NULL pointer dereference in
VFS follow_automount() when traversing a DFS referral link:
BUG: kernel NULL pointer dereference, address: 0000000000000000
...
Call Trace:
<TASK>
__traverse_mounts+0xb5/0x220
? cifs_revalidate_mapping+0x65/0xc0 [cifs]
step_into+0x195/0x610
? lookup_fast+0xe2/0xf0
path_lookupat+0x64/0x140
filename_lookup+0xc2/0x140
? __create_object+0x299/0x380
? kmem_cache_alloc+0x119/0x220
? user_path_at_empty+0x31/0x50
user_path_at_empty+0x31/0x50
__x64_sys_chdir+0x2a/0xd0
? exit_to_user_mode_prepare+0xca/0x100
do_syscall_64+0x42/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
This fix adds an inline cifs_dfs_d_automount() {return -EREMOTE} handler
when CONFIG_CIFS_DFS_UPCALL is disabled. An alternative would be to
avoid flagging S_AUTOMOUNT, etc. without CONFIG_CIFS_DFS_UPCALL. This
approach was chosen as it provides more control over the error path.
Signed-off-by: David Disseldorp <ddiss@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
Reviewed-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/cifs/cifsfs.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -125,7 +125,10 @@ extern const struct dentry_operations ci
#ifdef CONFIG_CIFS_DFS_UPCALL
extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
#else
-#define cifs_dfs_d_automount NULL
+static inline struct vfsmount *cifs_dfs_d_automount(struct path *path)
+{
+ return ERR_PTR(-EREMOTE);
+}
#endif
/* Functions related to symlinks */
Patches currently in stable-queue which might be from ddiss@xxxxxxx are
queue-5.4/cifs-fix-dfs-traversal-oops-without-config_cifs_dfs_upcall.patch
