From 179a88a8558bbf42991d361595281f3e45d7edfc Mon Sep 17 00:00:00 2001 From: David Disseldorp Date: Wed, 29 Mar 2023 22:24:06 +0200 Subject: 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: __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 Cc: stable@vger.kernel.org Reviewed-by: Paulo Alcantara (SUSE) Reviewed-by: Ronnie Sahlberg Signed-off-by: Steve French --- fs/cifs/cifsfs.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) 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 */ -- cgit v1.2.3 From 6cc041e90c178955219dcee4030bd5423f800f10 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Wed, 29 Mar 2023 17:14:21 -0300 Subject: cifs: avoid races in parallel reconnects in smb1 Prevent multiple threads of doing negotiate, session setup and tree connect by holding @ses->session_mutex in cifs_reconnect_tcon() while reconnecting session and tcon. Signed-off-by: Paulo Alcantara (SUSE) Reviewed-by: Ronnie Sahlberg Signed-off-by: Steve French --- fs/cifs/cifssmb.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c index 38a697eca305..c9d57ba84be4 100644 --- a/fs/cifs/cifssmb.c +++ b/fs/cifs/cifssmb.c @@ -71,7 +71,7 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command) int rc; struct cifs_ses *ses; struct TCP_Server_Info *server; - struct nls_table *nls_codepage; + struct nls_table *nls_codepage = NULL; /* * SMBs NegProt, SessSetup, uLogoff do not have tcon yet so check for @@ -99,6 +99,7 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command) } spin_unlock(&tcon->tc_lock); +again: rc = cifs_wait_for_server_reconnect(server, tcon->retry); if (rc) return rc; @@ -110,8 +111,7 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command) } spin_unlock(&ses->chan_lock); - nls_codepage = load_nls_default(); - + mutex_lock(&ses->session_mutex); /* * Recheck after acquire mutex. If another thread is negotiating * and the server never sends an answer the socket will be closed @@ -120,29 +120,38 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command) spin_lock(&server->srv_lock); if (server->tcpStatus == CifsNeedReconnect) { spin_unlock(&server->srv_lock); + mutex_lock(&ses->session_mutex); + + if (tcon->retry) + goto again; rc = -EHOSTDOWN; goto out; } spin_unlock(&server->srv_lock); + nls_codepage = load_nls_default(); + /* * need to prevent multiple threads trying to simultaneously * reconnect the same SMB session */ + spin_lock(&ses->ses_lock); spin_lock(&ses->chan_lock); - if (!cifs_chan_needs_reconnect(ses, server)) { + if (!cifs_chan_needs_reconnect(ses, server) && + ses->ses_status == SES_GOOD) { spin_unlock(&ses->chan_lock); + spin_unlock(&ses->ses_lock); /* this means that we only need to tree connect */ if (tcon->need_reconnect) goto skip_sess_setup; - rc = -EHOSTDOWN; + mutex_unlock(&ses->session_mutex); goto out; } spin_unlock(&ses->chan_lock); + spin_unlock(&ses->ses_lock); - mutex_lock(&ses->session_mutex); rc = cifs_negotiate_protocol(0, ses, server); if (!rc) rc = cifs_setup_session(0, ses, server, nls_codepage); -- cgit v1.2.3 From 09ba47b44d26b475bbdf9c80db9e0193d2b58956 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Wed, 29 Mar 2023 17:14:22 -0300 Subject: cifs: prevent infinite recursion in CIFSGetDFSRefer() We can't call smb_init() in CIFSGetDFSRefer() as cifs_reconnect_tcon() may end up calling CIFSGetDFSRefer() again to get new DFS referrals and thus causing an infinite recursion. Signed-off-by: Paulo Alcantara (SUSE) Reviewed-by: Ronnie Sahlberg Cc: stable@vger.kernel.org # 6.2 Signed-off-by: Steve French --- fs/cifs/cifssmb.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c index c9d57ba84be4..0d30b17494e4 100644 --- a/fs/cifs/cifssmb.c +++ b/fs/cifs/cifssmb.c @@ -4382,8 +4382,13 @@ CIFSGetDFSRefer(const unsigned int xid, struct cifs_ses *ses, return -ENODEV; getDFSRetry: - rc = smb_init(SMB_COM_TRANSACTION2, 15, ses->tcon_ipc, (void **) &pSMB, - (void **) &pSMBr); + /* + * Use smb_init_no_reconnect() instead of smb_init() as + * CIFSGetDFSRefer() may be called from cifs_reconnect_tcon() and thus + * causing an infinite recursion. + */ + rc = smb_init_no_reconnect(SMB_COM_TRANSACTION2, 15, ses->tcon_ipc, + (void **)&pSMB, (void **)&pSMBr); if (rc) return rc; -- cgit v1.2.3 From e03677100707f849f01d8faf07ee58b4e56cdbf1 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Wed, 29 Mar 2023 17:14:23 -0300 Subject: cifs: get rid of dead check in smb2_reconnect() The SMB2_IOCTL check in the switch statement will never be true as we return earlier from smb2_reconnect() if @smb2_command == SMB2_IOCTL. Signed-off-by: Paulo Alcantara (SUSE) Reviewed-by: Ronnie Sahlberg Signed-off-by: Steve French --- fs/cifs/smb2pdu.c | 1 - 1 file changed, 1 deletion(-) diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index 6bd2aa6af18f..2b92132097dc 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -310,7 +310,6 @@ out: case SMB2_READ: case SMB2_WRITE: case SMB2_LOCK: - case SMB2_IOCTL: case SMB2_QUERY_DIRECTORY: case SMB2_CHANGE_NOTIFY: case SMB2_QUERY_INFO: -- cgit v1.2.3