From: Henrique Carvalho <henrique.carvalho@suse.com>
To: sfrench@samba.org
Cc: metze@samba.org, pc@manguebit.org, ronniesahlberg@gmail.com,
sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com,
ematsumiya@suse.de, linux-cifs@vger.kernel.org,
stable@vger.kernel.org
Subject: [PATCH 2/3] smb: client: fix race in multichannel rescaling during mount
Date: Wed, 29 Apr 2026 17:52:35 -0300 [thread overview]
Message-ID: <20260429205236.456099-2-henrique.carvalho@suse.com> (raw)
In-Reply-To: <20260429205236.456099-1-henrique.carvalho@suse.com>
mchan_mount_* introduced async channel rescaling during mount. That can
lead race with other mount/remount attempts that use the same session,
when these are scaling down the channels, potentially leading to UAF, as
described in
https://lore.kernel.org/linux-cifs/rw7ptbx22cntes5eag5r3kvg5mzfvvzdhj4v2kw6mnunmsewev@f2iyrmmitkl3/
Fix this by using the same serialization used in other rescaling paths
and if in a race, rescheduling the channel scaling work.
Cc: stable@vger.kernel.org
Fixes: 556bb341f9f2 ("smb: client: introduce multichannel async work during mount")
Signed-off-by: Henrique Carvalho <henrique.carvalho@suse.com>
---
fs/smb/client/cifsglob.h | 2 +-
fs/smb/client/connect.c | 32 +++++++++++++++++++++++++-------
fs/smb/client/sess.c | 1 -
3 files changed, 26 insertions(+), 9 deletions(-)
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 82e0adc1dabd..ef63a1c3249c 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1817,7 +1817,7 @@ struct cifs_mount_ctx {
};
struct mchan_mount {
- struct work_struct work;
+ struct delayed_work dwork;
struct cifs_ses *ses;
};
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index dcde25da468d..2ea93f0b78c9 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -3813,7 +3813,7 @@ mchan_mount_alloc(struct cifs_ses *ses)
if (!mchan_mount)
return ERR_PTR(-ENOMEM);
- INIT_WORK(&mchan_mount->work, mchan_mount_work_fn);
+ INIT_DELAYED_WORK(&mchan_mount->dwork, mchan_mount_work_fn);
spin_lock(&cifs_tcp_ses_lock);
cifs_smb_ses_inc_refcount(ses);
@@ -3833,13 +3833,32 @@ mchan_mount_free(struct mchan_mount *mchan_mount)
static void
mchan_mount_work_fn(struct work_struct *work)
{
- struct mchan_mount *mchan_mount = container_of(work, struct mchan_mount, work);
+ struct mchan_mount *mchan_mount = container_of(work, struct mchan_mount, dwork.work);
+ struct cifs_ses *ses = mchan_mount->ses;
- smb3_update_ses_channels(mchan_mount->ses,
- mchan_mount->ses->server,
+ /*
+ * mchan_mount_work_fn could race with smb3_update_ses_channel called
+ * for the same session on remount, other mounts or
+ * smb3_update_ses_channel
+ */
+ spin_lock(&ses->ses_lock);
+ if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS) {
+ spin_unlock(&ses->ses_lock);
+ queue_delayed_work(cifsiod_wq, &mchan_mount->dwork, 2 * HZ);
+ return;
+ }
+ ses->flags |= CIFS_SES_FLAG_SCALE_CHANNELS;
+ spin_unlock(&ses->ses_lock);
+
+ smb3_update_ses_channels(ses,
+ ses->server,
false /* from_reconnect */,
false /* disable_mchan */);
+ spin_lock(&ses->ses_lock);
+ ses->flags &= ~CIFS_SES_FLAG_SCALE_CHANNELS;
+ spin_unlock(&ses->ses_lock);
+
mchan_mount_free(mchan_mount);
}
@@ -3885,7 +3904,7 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
goto error;
if (ctx->multichannel)
- queue_work(cifsiod_wq, &mchan_mount->work);
+ queue_work(cifsiod_wq, &mchan_mount->dwork.work);
free_xid(mnt_ctx.xid);
return rc;
@@ -3942,8 +3961,7 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
goto error;
if (ctx->multichannel)
- queue_work(cifsiod_wq, &mchan_mount->work);
-
+ queue_work(cifsiod_wq, &mchan_mount->dwork.work);
free_xid(mnt_ctx.xid);
return rc;
diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c
index de2012cc9cf3..24d5206e5c44 100644
--- a/fs/smb/client/sess.c
+++ b/fs/smb/client/sess.c
@@ -627,7 +627,6 @@ cifs_ses_add_channel(struct cifs_ses *ses,
return rc;
}
-
int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,
struct cifs_ses *ses)
{
--
2.53.0
next prev parent reply other threads:[~2026-04-29 20:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-29 20:52 [PATCH 1/3] smb: client: fix conflicting option validation for new mount API Henrique Carvalho
2026-04-29 20:52 ` Henrique Carvalho [this message]
2026-04-29 20:52 ` [PATCH 3/3] smb: client: make smb3_update_ses_channels() match expected API Henrique Carvalho
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