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cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL
commit 179a88a855
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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
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commit
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1 changed files with 4 additions and 1 deletions
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@ -121,7 +121,10 @@ extern const struct dentry_operations cifs_ci_dentry_ops;
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#ifdef CONFIG_CIFS_DFS_UPCALL
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extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
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#else
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#define cifs_dfs_d_automount NULL
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static inline struct vfsmount *cifs_dfs_d_automount(struct path *path)
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{
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return ERR_PTR(-EREMOTE);
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}
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#endif
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/* Functions related to symlinks */
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