From cc391b694ff085f62f133e6b8f864d43a8e69dfd Mon Sep 17 00:00:00 2001 From: Vincent Whitchurch Date: Wed, 1 Jun 2022 00:03:18 -0500 Subject: [PATCH] cifs: fix potential deadlock in direct reclaim The srv_mutex is used during writeback so cifs should ensure that allocations done when that mutex is held are done with GFP_NOFS, to avoid having direct reclaim ending up waiting for the same mutex and causing a deadlock. This is detected by lockdep with the splat below: ====================================================== WARNING: possible circular locking dependency detected 5.18.0 #70 Not tainted ------------------------------------------------------ kswapd0/49 is trying to acquire lock: ffff8880195782e0 (&tcp_ses->srv_mutex){+.+.}-{3:3}, at: compound_send_recv but task is already holding lock: ffffffffa98e66c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}-{0:0}: fs_reclaim_acquire kmem_cache_alloc_trace __request_module crypto_alg_mod_lookup crypto_alloc_tfm_node crypto_alloc_shash cifs_alloc_hash smb311_crypto_shash_allocate smb311_update_preauth_hash compound_send_recv cifs_send_recv SMB2_negotiate smb2_negotiate cifs_negotiate_protocol cifs_get_smb_ses cifs_mount cifs_smb3_do_mount smb3_get_tree vfs_get_tree path_mount __x64_sys_mount do_syscall_64 entry_SYSCALL_64_after_hwframe -> #0 (&tcp_ses->srv_mutex){+.+.}-{3:3}: __lock_acquire lock_acquire __mutex_lock mutex_lock_nested compound_send_recv cifs_send_recv SMB2_write smb2_sync_write cifs_write cifs_writepage_locked cifs_writepage shrink_page_list shrink_lruvec shrink_node balance_pgdat kswapd kthread ret_from_fork other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&tcp_ses->srv_mutex); lock(fs_reclaim); lock(&tcp_ses->srv_mutex); *** DEADLOCK *** 1 lock held by kswapd0/49: #0: ffffffffa98e66c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat stack backtrace: CPU: 2 PID: 49 Comm: kswapd0 Not tainted 5.18.0 #70 Call Trace: dump_stack_lvl dump_stack print_circular_bug.cold check_noncircular __lock_acquire lock_acquire __mutex_lock mutex_lock_nested compound_send_recv cifs_send_recv SMB2_write smb2_sync_write cifs_write cifs_writepage_locked cifs_writepage shrink_page_list shrink_lruvec shrink_node balance_pgdat kswapd kthread ret_from_fork Fix this by using the memalloc_nofs_save/restore APIs around the places where the srv_mutex is held. Do this in a wrapper function for the lock/unlock of the srv_mutex, and rename the srv_mutex to avoid missing call sites in the conversion. Note that there is another lockdep warning involving internal crypto locks, which was masked by this problem and is visible after this fix, see the discussion in this thread: https://lore.kernel.org/all/20220523123755.GA13668@axis.com/ Link: https://lore.kernel.org/r/CANT5p=rqcYfYMVHirqvdnnca4Mo+JQSw5Qu12v=kPfpk5yhhmg@mail.gmail.com/ Reported-by: Shyam Prasad N Suggested-by: Lars Persson Reviewed-by: Ronnie Sahlberg Reviewed-by: Enzo Matsumiya Signed-off-by: Vincent Whitchurch Signed-off-by: Steve French --- fs/cifs/cifs_swn.c | 4 ++-- fs/cifs/cifsencrypt.c | 8 ++++---- fs/cifs/cifsglob.h | 20 +++++++++++++++++++- fs/cifs/connect.c | 26 +++++++++++++------------- fs/cifs/dfs_cache.c | 4 ++-- fs/cifs/sess.c | 6 +++--- fs/cifs/smb1ops.c | 6 +++--- fs/cifs/smb2pdu.c | 6 +++--- fs/cifs/smbdirect.c | 4 ++-- fs/cifs/transport.c | 40 ++++++++++++++++++++-------------------- 10 files changed, 71 insertions(+), 53 deletions(-) diff --git a/fs/cifs/cifs_swn.c b/fs/cifs/cifs_swn.c index 180c234c2f46c2..1e4c7cc5287f03 100644 --- a/fs/cifs/cifs_swn.c +++ b/fs/cifs/cifs_swn.c @@ -465,7 +465,7 @@ static int cifs_swn_reconnect(struct cifs_tcon *tcon, struct sockaddr_storage *a int ret = 0; /* Store the reconnect address */ - mutex_lock(&tcon->ses->server->srv_mutex); + cifs_server_lock(tcon->ses->server); if (cifs_sockaddr_equal(&tcon->ses->server->dstaddr, addr)) goto unlock; @@ -501,7 +501,7 @@ static int cifs_swn_reconnect(struct cifs_tcon *tcon, struct sockaddr_storage *a cifs_signal_cifsd_for_reconnect(tcon->ses->server, false); unlock: - mutex_unlock(&tcon->ses->server->srv_mutex); + cifs_server_unlock(tcon->ses->server); return ret; } diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c index 0912d8bbbac14a..663cb9db49085b 100644 --- a/fs/cifs/cifsencrypt.c +++ b/fs/cifs/cifsencrypt.c @@ -236,9 +236,9 @@ int cifs_verify_signature(struct smb_rqst *rqst, cpu_to_le32(expected_sequence_number); cifs_pdu->Signature.Sequence.Reserved = 0; - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); rc = cifs_calc_signature(rqst, server, what_we_think_sig_should_be); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); if (rc) return rc; @@ -626,7 +626,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp) memcpy(ses->auth_key.response + baselen, tiblob, tilen); - mutex_lock(&ses->server->srv_mutex); + cifs_server_lock(ses->server); rc = cifs_alloc_hash("hmac(md5)", &ses->server->secmech.hmacmd5, @@ -678,7 +678,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp) cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__); unlock: - mutex_unlock(&ses->server->srv_mutex); + cifs_server_unlock(ses->server); setup_ntlmv2_rsp_ret: kfree(tiblob); diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 68da230c7f1128..d589e687611d05 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -16,6 +16,7 @@ #include #include #include +#include #include #include "cifs_fs_sb.h" #include "cifsacl.h" @@ -628,7 +629,8 @@ struct TCP_Server_Info { unsigned int in_flight; /* number of requests on the wire to server */ unsigned int max_in_flight; /* max number of requests that were on wire */ spinlock_t req_lock; /* protect the two values above */ - struct mutex srv_mutex; + struct mutex _srv_mutex; + unsigned int nofs_flag; struct task_struct *tsk; char server_GUID[16]; __u16 sec_mode; @@ -743,6 +745,22 @@ struct TCP_Server_Info { #endif }; +static inline void cifs_server_lock(struct TCP_Server_Info *server) +{ + unsigned int nofs_flag = memalloc_nofs_save(); + + mutex_lock(&server->_srv_mutex); + server->nofs_flag = nofs_flag; +} + +static inline void cifs_server_unlock(struct TCP_Server_Info *server) +{ + unsigned int nofs_flag = server->nofs_flag; + + mutex_unlock(&server->_srv_mutex); + memalloc_nofs_restore(nofs_flag); +} + struct cifs_credits { unsigned int value; unsigned int instance; diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index f54409f6370aef..d46702f5a6630c 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -148,7 +148,7 @@ static void cifs_resolve_server(struct work_struct *work) struct TCP_Server_Info *server = container_of(work, struct TCP_Server_Info, resolve.work); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); /* * Resolve the hostname again to make sure that IP address is up-to-date. @@ -159,7 +159,7 @@ static void cifs_resolve_server(struct work_struct *work) __func__, rc); } - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); } /* @@ -267,7 +267,7 @@ cifs_abort_connection(struct TCP_Server_Info *server) /* do not want to be sending data on a socket we are freeing */ cifs_dbg(FYI, "%s: tearing down socket\n", __func__); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); if (server->ssocket) { cifs_dbg(FYI, "State: 0x%x Flags: 0x%lx\n", server->ssocket->state, server->ssocket->flags); @@ -296,7 +296,7 @@ cifs_abort_connection(struct TCP_Server_Info *server) mid->mid_flags |= MID_DELETED; } spin_unlock(&GlobalMid_Lock); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); list_for_each_entry_safe(mid, nmid, &retry_list, qhead) { @@ -306,9 +306,9 @@ cifs_abort_connection(struct TCP_Server_Info *server) } if (cifs_rdma_enabled(server)) { - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); smbd_destroy(server); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); } } @@ -359,7 +359,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server, do { try_to_freeze(); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); if (!cifs_swn_set_server_dstaddr(server)) { /* resolve the hostname again to make sure that IP address is up-to-date */ @@ -372,7 +372,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server, else rc = generic_ip_connect(server); if (rc) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); cifs_dbg(FYI, "%s: reconnect error %d\n", __func__, rc); msleep(3000); } else { @@ -383,7 +383,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server, server->tcpStatus = CifsNeedNegotiate; spin_unlock(&cifs_tcp_ses_lock); cifs_swn_reset_server_dstaddr(server); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); mod_delayed_work(cifsiod_wq, &server->reconnect, 0); } } while (server->tcpStatus == CifsNeedReconnect); @@ -488,12 +488,12 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server) do { try_to_freeze(); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); rc = reconnect_target_unlocked(server, &tl, &target_hint); if (rc) { /* Failed to reconnect socket */ - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); cifs_dbg(FYI, "%s: reconnect error %d\n", __func__, rc); msleep(3000); continue; @@ -510,7 +510,7 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server) server->tcpStatus = CifsNeedNegotiate; spin_unlock(&cifs_tcp_ses_lock); cifs_swn_reset_server_dstaddr(server); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); mod_delayed_work(cifsiod_wq, &server->reconnect, 0); } while (server->tcpStatus == CifsNeedReconnect); @@ -1565,7 +1565,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx, init_waitqueue_head(&tcp_ses->response_q); init_waitqueue_head(&tcp_ses->request_q); INIT_LIST_HEAD(&tcp_ses->pending_mid_q); - mutex_init(&tcp_ses->srv_mutex); + mutex_init(&tcp_ses->_srv_mutex); memcpy(tcp_ses->workstation_RFC1001_name, ctx->source_rfc1001_name, RFC1001_NAME_LEN_WITH_NULL); memcpy(tcp_ses->server_RFC1001_name, diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c index c5dd6f7305bd16..aa7d00b5b3e7cc 100644 --- a/fs/cifs/dfs_cache.c +++ b/fs/cifs/dfs_cache.c @@ -1327,9 +1327,9 @@ static bool target_share_equal(struct TCP_Server_Info *server, const char *s1, c cifs_dbg(VFS, "%s: failed to convert address \'%s\'. skip address matching.\n", __func__, ip); } else { - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); match = cifs_match_ipaddr((struct sockaddr *)&server->dstaddr, &sa); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); } kfree(ip); diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c index c6214cfc575f3b..3b7915af1f62e6 100644 --- a/fs/cifs/sess.c +++ b/fs/cifs/sess.c @@ -1120,14 +1120,14 @@ sess_establish_session(struct sess_data *sess_data) struct cifs_ses *ses = sess_data->ses; struct TCP_Server_Info *server = sess_data->server; - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); if (!server->session_estab) { if (server->sign) { server->session_key.response = kmemdup(ses->auth_key.response, ses->auth_key.len, GFP_KERNEL); if (!server->session_key.response) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); return -ENOMEM; } server->session_key.len = @@ -1136,7 +1136,7 @@ sess_establish_session(struct sess_data *sess_data) server->sequence_number = 0x2; server->session_estab = true; } - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); cifs_dbg(FYI, "CIFS session established successfully\n"); return 0; diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c index c71c9a44bef4bb..2e20ee4dab7b7f 100644 --- a/fs/cifs/smb1ops.c +++ b/fs/cifs/smb1ops.c @@ -38,10 +38,10 @@ send_nt_cancel(struct TCP_Server_Info *server, struct smb_rqst *rqst, in_buf->WordCount = 0; put_bcc(0, in_buf); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); rc = cifs_sign_smb(in_buf, server, &mid->sequence_number); if (rc) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); return rc; } @@ -55,7 +55,7 @@ send_nt_cancel(struct TCP_Server_Info *server, struct smb_rqst *rqst, if (rc < 0) server->sequence_number--; - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); cifs_dbg(FYI, "issued NT_CANCEL for mid %u, rc = %d\n", get_mid(in_buf), rc); diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index 084be3a901980d..0e8c8524957912 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -1369,13 +1369,13 @@ SMB2_sess_establish_session(struct SMB2_sess_data *sess_data) struct cifs_ses *ses = sess_data->ses; struct TCP_Server_Info *server = sess_data->server; - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); if (server->ops->generate_signingkey) { rc = server->ops->generate_signingkey(ses, server); if (rc) { cifs_dbg(FYI, "SMB3 session key generation failed\n"); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); return rc; } } @@ -1383,7 +1383,7 @@ SMB2_sess_establish_session(struct SMB2_sess_data *sess_data) server->sequence_number = 0x2; server->session_estab = true; } - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); cifs_dbg(FYI, "SMB2/3 session established successfully\n"); return rc; diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c index c3278db1cade12..5fbbec22bcc8ba 100644 --- a/fs/cifs/smbdirect.c +++ b/fs/cifs/smbdirect.c @@ -1382,9 +1382,9 @@ void smbd_destroy(struct TCP_Server_Info *server) log_rdma_event(INFO, "freeing mr list\n"); wake_up_interruptible_all(&info->wait_mr); while (atomic_read(&info->mr_used_count)) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); msleep(1000); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); } destroy_mr_list(info); diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c index 05eca41e3b1e09..bfc9bd55870a06 100644 --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -822,7 +822,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst, } else instance = exist_credits->instance; - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); /* * We can't use credits obtained from the previous session to send this @@ -830,14 +830,14 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst, * return -EAGAIN in such cases to let callers handle it. */ if (instance != server->reconnect_instance) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); add_credits_and_wake_if(server, &credits, optype); return -EAGAIN; } mid = server->ops->setup_async_request(server, rqst); if (IS_ERR(mid)) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); add_credits_and_wake_if(server, &credits, optype); return PTR_ERR(mid); } @@ -868,7 +868,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst, cifs_delete_mid(mid); } - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); if (rc == 0) return 0; @@ -1109,7 +1109,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, * of smb data. */ - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); /* * All the parts of the compound chain belong obtained credits from the @@ -1119,7 +1119,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, * handle it. */ if (instance != server->reconnect_instance) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); for (j = 0; j < num_rqst; j++) add_credits(server, &credits[j], optype); return -EAGAIN; @@ -1131,7 +1131,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, revert_current_mid(server, i); for (j = 0; j < i; j++) cifs_delete_mid(midQ[j]); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); /* Update # of requests on wire to server */ for (j = 0; j < num_rqst; j++) @@ -1163,7 +1163,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, server->sequence_number -= 2; } - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); /* * If sending failed for some reason or it is an oplock break that we @@ -1190,9 +1190,9 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, if ((ses->ses_status == SES_NEW) || (optype & CIFS_NEG_OP) || (optype & CIFS_SESS_OP)) { spin_unlock(&cifs_tcp_ses_lock); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); smb311_update_preauth_hash(ses, server, rqst[0].rq_iov, rqst[0].rq_nvec); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); spin_lock(&cifs_tcp_ses_lock); } @@ -1266,9 +1266,9 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, .iov_len = resp_iov[0].iov_len }; spin_unlock(&cifs_tcp_ses_lock); - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); smb311_update_preauth_hash(ses, server, &iov, 1); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); spin_lock(&cifs_tcp_ses_lock); } spin_unlock(&cifs_tcp_ses_lock); @@ -1385,11 +1385,11 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses, and avoid races inside tcp sendmsg code that could cause corruption of smb data */ - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); rc = allocate_mid(ses, in_buf, &midQ); if (rc) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); /* Update # of requests on wire to server */ add_credits(server, &credits, 0); return rc; @@ -1397,7 +1397,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses, rc = cifs_sign_smb(in_buf, server, &midQ->sequence_number); if (rc) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); goto out; } @@ -1411,7 +1411,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses, if (rc < 0) server->sequence_number -= 2; - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); if (rc < 0) goto out; @@ -1530,18 +1530,18 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon, and avoid races inside tcp sendmsg code that could cause corruption of smb data */ - mutex_lock(&server->srv_mutex); + cifs_server_lock(server); rc = allocate_mid(ses, in_buf, &midQ); if (rc) { - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); return rc; } rc = cifs_sign_smb(in_buf, server, &midQ->sequence_number); if (rc) { cifs_delete_mid(midQ); - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); return rc; } @@ -1554,7 +1554,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon, if (rc < 0) server->sequence_number -= 2; - mutex_unlock(&server->srv_mutex); + cifs_server_unlock(server); if (rc < 0) { cifs_delete_mid(midQ);