* [PATCH 6.15 112/263] smb: client: fix regression with native SMB symlinks
[not found] <20250703144004.276210867@linuxfoundation.org>
@ 2025-07-03 14:40 ` Greg Kroah-Hartman
2025-07-03 14:41 ` [PATCH 6.15 170/263] smb: client: fix potential deadlock when reconnecting channels Greg Kroah-Hartman
1 sibling, 0 replies; 2+ messages in thread
From: Greg Kroah-Hartman @ 2025-07-03 14:40 UTC (permalink / raw)
To: stable
Cc: Greg Kroah-Hartman, patches, linux-cifs, Remy Monsen,
Pierguido Lambri, Paulo Alcantara (Red Hat), Steve French
6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paulo Alcantara <pc@manguebit.org>
commit ff8abbd248c1f52df0c321690b88454b13ff54b2 upstream.
Some users and customers reported that their backup/copy tools started
to fail when the directory being copied contained symlink targets that
the client couldn't parse - even when those symlinks weren't followed.
Fix this by allowing lstat(2) and readlink(2) to succeed even when the
client can't resolve the symlink target, restoring old behavior.
Cc: linux-cifs@vger.kernel.org
Cc: stable@vger.kernel.org
Reported-by: Remy Monsen <monsen@monsen.cc>
Closes: https://lore.kernel.org/r/CAN+tdP7y=jqw3pBndZAGjQv0ObFq8Q=+PUDHgB36HdEz9QA6FQ@mail.gmail.com
Reported-by: Pierguido Lambri <plambri@redhat.com>
Fixes: 12b466eb52d9 ("cifs: Fix creating and resolving absolute NT-style symlinks")
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/smb/client/reparse.c | 20 ++++----------------
1 file changed, 4 insertions(+), 16 deletions(-)
diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 511611206dab..1c40e42e4d89 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -875,15 +875,8 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len,
abs_path += sizeof("\\DosDevices\\")-1;
else if (strstarts(abs_path, "\\GLOBAL??\\"))
abs_path += sizeof("\\GLOBAL??\\")-1;
- else {
- /* Unhandled absolute symlink, points outside of DOS/Win32 */
- cifs_dbg(VFS,
- "absolute symlink '%s' cannot be converted from NT format "
- "because points to unknown target\n",
- smb_target);
- rc = -EIO;
- goto out;
- }
+ else
+ goto out_unhandled_target;
/* Sometimes path separator after \?? is double backslash */
if (abs_path[0] == '\\')
@@ -910,13 +903,7 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len,
abs_path++;
abs_path[0] = drive_letter;
} else {
- /* Unhandled absolute symlink. Report an error. */
- cifs_dbg(VFS,
- "absolute symlink '%s' cannot be converted from NT format "
- "because points to unknown target\n",
- smb_target);
- rc = -EIO;
- goto out;
+ goto out_unhandled_target;
}
abs_path_len = strlen(abs_path)+1;
@@ -966,6 +953,7 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len,
* These paths have same format as Linux symlinks, so no
* conversion is needed.
*/
+out_unhandled_target:
linux_target = smb_target;
smb_target = NULL;
}
--
2.50.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH 6.15 170/263] smb: client: fix potential deadlock when reconnecting channels
[not found] <20250703144004.276210867@linuxfoundation.org>
2025-07-03 14:40 ` [PATCH 6.15 112/263] smb: client: fix regression with native SMB symlinks Greg Kroah-Hartman
@ 2025-07-03 14:41 ` Greg Kroah-Hartman
1 sibling, 0 replies; 2+ messages in thread
From: Greg Kroah-Hartman @ 2025-07-03 14:41 UTC (permalink / raw)
To: stable
Cc: Greg Kroah-Hartman, patches, linux-cifs, David Howells,
Paulo Alcantara (Red Hat), Steve French, Sasha Levin
6.15-stable review patch. If anyone has any objections, please let me know.
------------------
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 214e53acf72a8..56381cbb63990 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -709,6 +709,7 @@ 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 f9aef60f1901a..e92c7b71626fd 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -124,6 +124,14 @@ 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
@@ -137,39 +145,45 @@ 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);
+ }
}
/*
--
2.39.5
^ permalink raw reply related [flat|nested] 2+ messages in thread