Commit 15a12fbb authored by Pavel Shilovsky's avatar Pavel Shilovsky Committed by Sasha Levin

CIFS: Fix a possible memory corruption during reconnect

[ Upstream commit 53e0e11e ]

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 <stable@vger.kernel.org>
Signed-off-by: default avatarPavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
parent 51fce08b
......@@ -615,6 +615,8 @@ struct TCP_Server_Info {
#ifdef CONFIG_CIFS_SMB2
unsigned int max_read;
unsigned int max_write;
struct delayed_work reconnect; /* reconnect workqueue job */
struct mutex reconnect_mutex; /* prevent simultaneous reconnects */
#endif /* CONFIG_CIFS_SMB2 */
};
......@@ -814,6 +816,7 @@ cap_unix(struct cifs_ses *ses)
struct cifs_tcon {
struct list_head tcon_list;
int tc_count;
struct list_head rlist; /* reconnect list */
struct list_head openFileList;
struct cifs_ses *ses; /* pointer to session associated with */
char treeName[MAX_TREE_SIZE + 1]; /* UNC name of resource in ASCII */
......
......@@ -207,6 +207,9 @@ extern void cifs_add_pending_open_locked(struct cifs_fid *fid,
struct tcon_link *tlink,
struct cifs_pending_open *open);
extern void cifs_del_pending_open(struct cifs_pending_open *open);
extern void cifs_put_tcp_session(struct TCP_Server_Info *server,
int from_reconnect);
extern void cifs_put_tcon(struct cifs_tcon *tcon);
#if IS_ENABLED(CONFIG_CIFS_DFS_UPCALL)
extern void cifs_dfs_release_automount_timer(void);
......
......@@ -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
......@@ -2069,8 +2072,8 @@ 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;
......@@ -2087,6 +2090,19 @@ 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);
......@@ -2151,6 +2167,10 @@ 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,
......@@ -2303,7 +2323,7 @@ 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
......@@ -2476,7 +2496,7 @@ 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;
}
......@@ -2566,7 +2586,7 @@ cifs_find_tcon(struct cifs_ses *ses, const char *unc)
return NULL;
}
static void
void
cifs_put_tcon(struct cifs_tcon *tcon)
{
unsigned int xid;
......@@ -3673,7 +3693,7 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
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);
}
......@@ -3984,7 +4004,7 @@ 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;
}
......
......@@ -1615,6 +1615,54 @@ smb2_echo_callback(struct mid_q_entry *mid)
add_credits(server, credits_received, CIFS_ECHO_OP);
}
void smb2_reconnect_server(struct work_struct *work)
{
struct TCP_Server_Info *server = container_of(work,
struct TCP_Server_Info, reconnect.work);
struct cifs_ses *ses;
struct cifs_tcon *tcon, *tcon2;
struct list_head tmp_list;
int tcon_exist = false;
/* Prevent simultaneous reconnects that can corrupt tcon->rlist list */
mutex_lock(&server->reconnect_mutex);
INIT_LIST_HEAD(&tmp_list);
cifs_dbg(FYI, "Need negotiate, reconnecting tcons\n");
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) {
tcon->tc_count++;
list_add_tail(&tcon->rlist, &tmp_list);
tcon_exist = true;
}
}
}
/*
* Get the reference to server struct to be sure that the last call of
* cifs_put_tcon() in the loop below won't release the server pointer.
*/
if (tcon_exist)
server->srv_count++;
spin_unlock(&cifs_tcp_ses_lock);
list_for_each_entry_safe(tcon, tcon2, &tmp_list, rlist) {
smb2_reconnect(SMB2_ECHO, tcon);
list_del_init(&tcon->rlist);
cifs_put_tcon(tcon);
}
cifs_dbg(FYI, "Reconnecting tcons finished\n");
mutex_unlock(&server->reconnect_mutex);
/* now we can safely release srv struct */
if (tcon_exist)
cifs_put_tcp_session(server, 1);
}
int
SMB2_echo(struct TCP_Server_Info *server)
{
......@@ -1627,32 +1675,11 @@ SMB2_echo(struct TCP_Server_Info *server)
cifs_dbg(FYI, "In echo request\n");
if (server->tcpStatus == CifsNeedNegotiate) {
struct list_head *tmp, *tmp2;
struct cifs_ses *ses;
struct cifs_tcon *tcon;
cifs_dbg(FYI, "Need negotiate, reconnecting tcons\n");
spin_lock(&cifs_tcp_ses_lock);
list_for_each(tmp, &server->smb_ses_list) {
ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
list_for_each(tmp2, &ses->tcon_list) {
tcon = list_entry(tmp2, struct cifs_tcon,
tcon_list);
/* add check for persistent handle reconnect */
if (tcon && tcon->need_reconnect) {
spin_unlock(&cifs_tcp_ses_lock);
rc = smb2_reconnect(SMB2_ECHO, tcon);
spin_lock(&cifs_tcp_ses_lock);
}
}
}
spin_unlock(&cifs_tcp_ses_lock);
/* No need to send echo on newly established connections */
queue_delayed_work(cifsiod_wq, &server->reconnect, 0);
return rc;
}
/* if no session, renegotiate failed above */
if (server->tcpStatus == CifsNeedNegotiate)
return -EIO;
rc = small_smb2_init(SMB2_ECHO, NULL, (void **)&req);
if (rc)
return rc;
......
......@@ -95,6 +95,7 @@ extern int smb2_open_file(const unsigned int xid,
extern int smb2_unlock_range(struct cifsFileInfo *cfile,
struct file_lock *flock, const unsigned int xid);
extern int smb2_push_mandatory_locks(struct cifsFileInfo *cfile);
extern void smb2_reconnect_server(struct work_struct *work);
/*
* SMB2 Worker functions - most of protocol specific implementation details
......
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