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authorDavid Disseldorp <ddiss@suse.de>2023-03-29 22:24:06 +0200
committerSteve French <stfrench@microsoft.com>2023-03-30 17:28:44 -0500
commit179a88a8558bbf42991d361595281f3e45d7edfc (patch)
tree5f403e1cb6397e0b2fe518ef0bd2a1676069bcd0
parent197b6b60ae7bc51dd0814953c562833143b292aa (diff)
cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL
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@suse.de> Cc: stable@vger.kernel.org Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com> Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com> Signed-off-by: Steve French <stfrench@microsoft.com>
-rw-r--r--fs/cifs/cifsfs.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 71fe0a0a7992..415176b2cf32 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -124,7 +124,10 @@ extern const struct dentry_operations cifs_ci_dentry_ops;
#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 */