6.6-stable review patch. If anyone has any objections, please let me know.
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From: Paulo Alcantara pc@manguebit.org
[ Upstream commit 711741f94ac3cf9f4e3aa73aa171e76d188c0819 ]
Fix cifs_signal_cifsd_for_reconnect() to take the correct lock order and prevent the following deadlock from happening
====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc3-build2+ #1301 Tainted: G S W ------------------------------------------------------ cifsd/6055 is trying to acquire lock: ffff88810ad56038 (&tcp_ses->srv_lock){+.+.}-{3:3}, at: cifs_signal_cifsd_for_reconnect+0x134/0x200
but task is already holding lock: ffff888119c64330 (&ret_buf->chan_lock){+.+.}-{3:3}, at: cifs_signal_cifsd_for_reconnect+0xcf/0x200
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&ret_buf->chan_lock){+.+.}-{3:3}: validate_chain+0x1cf/0x270 __lock_acquire+0x60e/0x780 lock_acquire.part.0+0xb4/0x1f0 _raw_spin_lock+0x2f/0x40 cifs_setup_session+0x81/0x4b0 cifs_get_smb_ses+0x771/0x900 cifs_mount_get_session+0x7e/0x170 cifs_mount+0x92/0x2d0 cifs_smb3_do_mount+0x161/0x460 smb3_get_tree+0x55/0x90 vfs_get_tree+0x46/0x180 do_new_mount+0x1b0/0x2e0 path_mount+0x6ee/0x740 do_mount+0x98/0xe0 __do_sys_mount+0x148/0x180 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #1 (&ret_buf->ses_lock){+.+.}-{3:3}: validate_chain+0x1cf/0x270 __lock_acquire+0x60e/0x780 lock_acquire.part.0+0xb4/0x1f0 _raw_spin_lock+0x2f/0x40 cifs_match_super+0x101/0x320 sget+0xab/0x270 cifs_smb3_do_mount+0x1e0/0x460 smb3_get_tree+0x55/0x90 vfs_get_tree+0x46/0x180 do_new_mount+0x1b0/0x2e0 path_mount+0x6ee/0x740 do_mount+0x98/0xe0 __do_sys_mount+0x148/0x180 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #0 (&tcp_ses->srv_lock){+.+.}-{3:3}: check_noncircular+0x95/0xc0 check_prev_add+0x115/0x2f0 validate_chain+0x1cf/0x270 __lock_acquire+0x60e/0x780 lock_acquire.part.0+0xb4/0x1f0 _raw_spin_lock+0x2f/0x40 cifs_signal_cifsd_for_reconnect+0x134/0x200 __cifs_reconnect+0x8f/0x500 cifs_handle_standard+0x112/0x280 cifs_demultiplex_thread+0x64d/0xbc0 kthread+0x2f7/0x310 ret_from_fork+0x2a/0x230 ret_from_fork_asm+0x1a/0x30
other info that might help us debug this:
Chain exists of: &tcp_ses->srv_lock --> &ret_buf->ses_lock --> &ret_buf->chan_lock
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&ret_buf->chan_lock); lock(&ret_buf->ses_lock); lock(&ret_buf->chan_lock); lock(&tcp_ses->srv_lock);
*** DEADLOCK ***
3 locks held by cifsd/6055: #0: ffffffff857de398 (&cifs_tcp_ses_lock){+.+.}-{3:3}, at: cifs_signal_cifsd_for_reconnect+0x7b/0x200 #1: ffff888119c64060 (&ret_buf->ses_lock){+.+.}-{3:3}, at: cifs_signal_cifsd_for_reconnect+0x9c/0x200 #2: ffff888119c64330 (&ret_buf->chan_lock){+.+.}-{3:3}, at: cifs_signal_cifsd_for_reconnect+0xcf/0x200
Cc: linux-cifs@vger.kernel.org Reported-by: David Howells dhowells@redhat.com Fixes: d7d7a66aacd6 ("cifs: avoid use of global locks for high contention data") Reviewed-by: David Howells dhowells@redhat.com Tested-by: David Howells dhowells@redhat.com Signed-off-by: Paulo Alcantara (Red Hat) pc@manguebit.org Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/smb/client/cifsglob.h | 1 + fs/smb/client/connect.c | 58 +++++++++++++++++++++++++--------------- 2 files changed, 37 insertions(+), 22 deletions(-)
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h index c7da6bf2f44be..d776340ad91ce 100644 --- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -677,6 +677,7 @@ inc_rfc1001_len(void *buf, int count) struct TCP_Server_Info { struct list_head tcp_ses_list; struct list_head smb_ses_list; + struct list_head rlist; /* reconnect list */ spinlock_t srv_lock; /* protect anything here that is not protected */ __u64 conn_id; /* connection identifier (useful for debugging) */ int srv_count; /* reference counter */ diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index 8fa5fe0a8c5c5..454420aa02220 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -140,6 +140,14 @@ static void smb2_query_server_interfaces(struct work_struct *work) (SMB_INTERFACE_POLL_INTERVAL * HZ)); }
+#define set_need_reco(server) \ +do { \ + spin_lock(&server->srv_lock); \ + if (server->tcpStatus != CifsExiting) \ + server->tcpStatus = CifsNeedReconnect; \ + spin_unlock(&server->srv_lock); \ +} while (0) + /* * Update the tcpStatus for the server. * This is used to signal the cifsd thread to call cifs_reconnect @@ -153,39 +161,45 @@ void cifs_signal_cifsd_for_reconnect(struct TCP_Server_Info *server, bool all_channels) { - struct TCP_Server_Info *pserver; + struct TCP_Server_Info *nserver; struct cifs_ses *ses; + LIST_HEAD(reco); int i;
- /* If server is a channel, select the primary channel */ - pserver = SERVER_IS_CHAN(server) ? server->primary_server : server; - /* if we need to signal just this channel */ if (!all_channels) { - spin_lock(&server->srv_lock); - if (server->tcpStatus != CifsExiting) - server->tcpStatus = CifsNeedReconnect; - spin_unlock(&server->srv_lock); + set_need_reco(server); return; }
- spin_lock(&cifs_tcp_ses_lock); - list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) { - if (cifs_ses_exiting(ses)) - continue; - spin_lock(&ses->chan_lock); - for (i = 0; i < ses->chan_count; i++) { - if (!ses->chans[i].server) + if (SERVER_IS_CHAN(server)) + server = server->primary_server; + scoped_guard(spinlock, &cifs_tcp_ses_lock) { + set_need_reco(server); + list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) { + spin_lock(&ses->ses_lock); + if (ses->ses_status == SES_EXITING) { + spin_unlock(&ses->ses_lock); continue; - - spin_lock(&ses->chans[i].server->srv_lock); - if (ses->chans[i].server->tcpStatus != CifsExiting) - ses->chans[i].server->tcpStatus = CifsNeedReconnect; - spin_unlock(&ses->chans[i].server->srv_lock); + } + spin_lock(&ses->chan_lock); + for (i = 1; i < ses->chan_count; i++) { + nserver = ses->chans[i].server; + if (!nserver) + continue; + nserver->srv_count++; + list_add(&nserver->rlist, &reco); + } + spin_unlock(&ses->chan_lock); + spin_unlock(&ses->ses_lock); } - spin_unlock(&ses->chan_lock); } - spin_unlock(&cifs_tcp_ses_lock); + + list_for_each_entry_safe(server, nserver, &reco, rlist) { + list_del_init(&server->rlist); + set_need_reco(server); + cifs_put_tcp_session(server, 0); + } }
/*