From 96a988ffeb90dba33a71c3826086fe67c897a183 Mon Sep 17 00:00:00 2001 From: Pavel Shilovsky Date: Tue, 29 Nov 2016 11:31:23 -0800 Subject: [PATCH] CIFS: Fix a possible double locking of mutex during reconnect With the current code it is possible to lock a mutex twice when a subsequent reconnects are triggered. On the 1st reconnect we reconnect sessions and tcons and then persistent file handles. If the 2nd reconnect happens during the reconnecting of persistent file handles then the following sequence of calls is observed: cifs_reopen_file -> SMB2_open -> small_smb2_init -> smb2_reconnect -> cifs_reopen_persistent_file_handles -> cifs_reopen_file (again!). So, we are trying to acquire the same cfile->fh_mutex twice which is wrong. Fix this by moving reconnecting of persistent handles to the delayed work (smb2_reconnect_server) and submitting this work every time we reconnect tcon in SMB2 commands handling codepath. This can also lead to corruption of a temporary file list in cifs_reopen_persistent_file_handles() because we can recursively call this function twice. Cc: Stable # v4.9+ Signed-off-by: Pavel Shilovsky --- fs/cifs/cifsglob.h | 1 + fs/cifs/file.c | 8 +++++++- fs/cifs/smb2pdu.c | 14 +++++++++----- fs/cifs/smb2pdu.h | 2 ++ 4 files changed, 19 insertions(+), 6 deletions(-) diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 89a0d7f17cc7..59ab5a29d256 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -926,6 +926,7 @@ struct cifs_tcon { bool broken_posix_open; /* e.g. Samba server versions < 3.3.2, 3.2.9 */ bool broken_sparse_sup; /* if server or share does not support sparse */ bool need_reconnect:1; /* connection reset, tid now invalid */ + bool need_reopen_files:1; /* need to reopen tcon file handles */ bool use_resilient:1; /* use resilient instead of durable handles */ bool use_persistent:1; /* use persistent instead of durable handles */ #ifdef CONFIG_CIFS_SMB2 diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 7f5f6176c6f1..18a1e1d6671f 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -777,6 +777,11 @@ cifs_reopen_persistent_handles(struct cifs_tcon *tcon) struct list_head *tmp1; struct list_head tmp_list; + if (!tcon->use_persistent || !tcon->need_reopen_files) + return; + + tcon->need_reopen_files = false; + cifs_dbg(FYI, "Reopen persistent handles"); INIT_LIST_HEAD(&tmp_list); @@ -793,7 +798,8 @@ cifs_reopen_persistent_handles(struct cifs_tcon *tcon) list_for_each_safe(tmp, tmp1, &tmp_list) { open_file = list_entry(tmp, struct cifsFileInfo, rlist); - cifs_reopen_file(open_file, false /* do not flush */); + if (cifs_reopen_file(open_file, false /* do not flush */)) + tcon->need_reopen_files = true; list_del_init(&open_file->rlist); cifsFileInfo_put(open_file); } diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index 4ba3f68a1766..87457227812c 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -250,16 +250,19 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon) } cifs_mark_open_files_invalid(tcon); + if (tcon->use_persistent) + tcon->need_reopen_files = true; rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nls_codepage); mutex_unlock(&tcon->ses->session_mutex); - if (tcon->use_persistent) - cifs_reopen_persistent_handles(tcon); - cifs_dbg(FYI, "reconnect tcon rc = %d\n", rc); if (rc) goto out; + + if (smb2_command != SMB2_INTERNAL_CMD) + queue_delayed_work(cifsiod_wq, &server->reconnect, 0); + atomic_inc(&tconInfoReconnectCount); out: /* @@ -1990,7 +1993,7 @@ void smb2_reconnect_server(struct work_struct *work) spin_lock(&cifs_tcp_ses_lock); list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) { list_for_each_entry(tcon, &ses->tcon_list, tcon_list) { - if (tcon->need_reconnect) { + if (tcon->need_reconnect || tcon->need_reopen_files) { tcon->tc_count++; list_add_tail(&tcon->rlist, &tmp_list); tcon_exist = true; @@ -2007,7 +2010,8 @@ void smb2_reconnect_server(struct work_struct *work) spin_unlock(&cifs_tcp_ses_lock); list_for_each_entry_safe(tcon, tcon2, &tmp_list, rlist) { - smb2_reconnect(SMB2_ECHO, tcon); + if (!smb2_reconnect(SMB2_INTERNAL_CMD, tcon)) + cifs_reopen_persistent_handles(tcon); list_del_init(&tcon->rlist); cifs_put_tcon(tcon); } diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h index fd3709e8de33..dc0d141f33e2 100644 --- a/fs/cifs/smb2pdu.h +++ b/fs/cifs/smb2pdu.h @@ -80,6 +80,8 @@ #define SMB2_SET_INFO cpu_to_le16(SMB2_SET_INFO_HE) #define SMB2_OPLOCK_BREAK cpu_to_le16(SMB2_OPLOCK_BREAK_HE) +#define SMB2_INTERNAL_CMD cpu_to_le16(0xFFFF) + #define NUMBER_OF_SMB2_COMMANDS 0x0013 /* BB FIXME - analyze following length BB */