From 53e0e11efe9289535b060a51d4cf37c25e0d0f2b Mon Sep 17 00:00:00 2001 From: Pavel Shilovsky Date: Fri, 4 Nov 2016 11:50:31 -0700 Subject: CIFS: Fix a possible memory corruption during reconnect We can not unlock/lock cifs_tcp_ses_lock while walking through ses and tcon lists because it can corrupt list iterator pointers and a tcon structure can be released if we don't hold an extra reference. Fix it by moving a reconnect process to a separate delayed work and acquiring a reference to every tcon that needs to be reconnected. Also do not send an echo request on newly established connections. CC: Stable Signed-off-by: Pavel Shilovsky --- fs/cifs/connect.c | 34 +++++++++++++++++++++++++++------- 1 file changed, 27 insertions(+), 7 deletions(-) (limited to 'fs/cifs/connect.c') diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 5563de3c64fd..5aaf7b1359a5 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -52,6 +52,9 @@ #include "nterr.h" #include "rfc1002pdu.h" #include "fscache.h" +#ifdef CONFIG_CIFS_SMB2 +#include "smb2proto.h" +#endif #define CIFS_PORT 445 #define RFC1001_PORT 139 @@ -2110,8 +2113,8 @@ cifs_find_tcp_session(struct smb_vol *vol) return NULL; } -static void -cifs_put_tcp_session(struct TCP_Server_Info *server) +void +cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect) { struct task_struct *task; @@ -2128,6 +2131,19 @@ cifs_put_tcp_session(struct TCP_Server_Info *server) cancel_delayed_work_sync(&server->echo); +#ifdef CONFIG_CIFS_SMB2 + if (from_reconnect) + /* + * Avoid deadlock here: reconnect work calls + * cifs_put_tcp_session() at its end. Need to be sure + * that reconnect work does nothing with server pointer after + * that step. + */ + cancel_delayed_work(&server->reconnect); + else + cancel_delayed_work_sync(&server->reconnect); +#endif + spin_lock(&GlobalMid_Lock); server->tcpStatus = CifsExiting; spin_unlock(&GlobalMid_Lock); @@ -2192,6 +2208,10 @@ cifs_get_tcp_session(struct smb_vol *volume_info) INIT_LIST_HEAD(&tcp_ses->tcp_ses_list); INIT_LIST_HEAD(&tcp_ses->smb_ses_list); INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request); +#ifdef CONFIG_CIFS_SMB2 + INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server); + mutex_init(&tcp_ses->reconnect_mutex); +#endif memcpy(&tcp_ses->srcaddr, &volume_info->srcaddr, sizeof(tcp_ses->srcaddr)); memcpy(&tcp_ses->dstaddr, &volume_info->dstaddr, @@ -2350,7 +2370,7 @@ cifs_put_smb_ses(struct cifs_ses *ses) spin_unlock(&cifs_tcp_ses_lock); sesInfoFree(ses); - cifs_put_tcp_session(server); + cifs_put_tcp_session(server, 0); } #ifdef CONFIG_KEYS @@ -2524,7 +2544,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info) mutex_unlock(&ses->session_mutex); /* existing SMB ses has a server reference already */ - cifs_put_tcp_session(server); + cifs_put_tcp_session(server, 0); free_xid(xid); return ses; } @@ -2620,7 +2640,7 @@ cifs_find_tcon(struct cifs_ses *ses, struct smb_vol *volume_info) return NULL; } -static void +void cifs_put_tcon(struct cifs_tcon *tcon) { unsigned int xid; @@ -3824,7 +3844,7 @@ mount_fail_check: else if (ses) cifs_put_smb_ses(ses); else - cifs_put_tcp_session(server); + cifs_put_tcp_session(server, 0); bdi_destroy(&cifs_sb->bdi); } @@ -4135,7 +4155,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid) ses = cifs_get_smb_ses(master_tcon->ses->server, vol_info); if (IS_ERR(ses)) { tcon = (struct cifs_tcon *)ses; - cifs_put_tcp_session(master_tcon->ses->server); + cifs_put_tcp_session(master_tcon->ses->server, 0); goto out; } -- cgit v1.2.3-55-g7522