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FAILED: patch "[PATCH] ksmbd: validate owner of durable handle on reconnect" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 2 messages Apr 20

Subsystems (2)
Stable branch Kernel SMB3 server (ksmbd)
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#0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 49110a8ce654bbe56bef7c5e44cce31f4b102b8a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026042010-daisy-antonym-6130@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 49110a8ce654bbe56bef7c5e44cce31f4b102b8a Mon Sep 17 00:00:00 2001
From: Namjae Jeon <[email protected]>
Date: Sun, 12 Apr 2026 22:16:16 +0900
Subject: [PATCH] ksmbd: validate owner of durable handle on reconnect

Currently, ksmbd does not verify if the user attempting to reconnect to a durable handle is the same user who originally opened the file. This allows any authenticated user to hijack an orphaned durable handle by predicting or brute-forcing the persistent ID.

According to MS-SMB2, the server MUST verify that the SecurityContext of the reconnect request matches the SecurityContext associated with the existing open.
Add a durable_owner structure to ksmbd_file to store the original opener's UID, GID, and account name. and catpure the owner information when a file handle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner() to validate the identity of the requester during SMB2_CREATE (DHnC).

Fixes c8efcc786146 ("ksmbd: add support for durable handles v1/v2")
Reported-by Davide Ornaghi <[email protected]>
Reported-by Navaneeth K <[email protected]>
Signed-off-by Namjae Jeon <[email protected]>
Signed-off-by Steve French <[email protected]>
fs/smb/server/mgmt/user_session.c +3 -5
index 39be2d2be86c..a86589408835 100644
@@ -382,12 +382,10 @@ void ksmbd_session_destroy(struct ksmbd_session *sess)
 		return;
 
 	delete_proc_session(sess);
-
+	ksmbd_tree_conn_session_logoff(sess);
+	ksmbd_destroy_file_table(sess);
 	if (sess->user)
 		ksmbd_free_user(sess->user);
-
-	ksmbd_tree_conn_session_logoff(sess);
-	ksmbd_destroy_file_table(&sess->file_table);
 	ksmbd_launch_ksmbd_durable_scavenger();
 	ksmbd_session_rpc_clear_list(sess);
 	free_channel_list(sess);

@@ -618,7 +616,7 @@ void destroy_previous_session(struct ksmbd_conn *conn,
 		goto out;
 	}
 
-	ksmbd_destroy_file_table(&prev_sess->file_table);
+	ksmbd_destroy_file_table(prev_sess);
 	prev_sess->state = SMB2_SESSION_EXPIRED;
 	ksmbd_all_conn_set_status(id, KSMBD_SESS_NEED_SETUP);
 	ksmbd_launch_ksmbd_durable_scavenger();
fs/smb/server/oplock.c +7 -0
index 9b2bb8764a80..cd3f28b0e7cb 100644
@@ -1841,6 +1841,7 @@ int smb2_check_durable_oplock(struct ksmbd_conn *conn,
 			      struct ksmbd_share_config *share,
 			      struct ksmbd_file *fp,
 			      struct lease_ctx_info *lctx,
+			      struct ksmbd_user *user,
 			      char *name)
 {
 	struct oplock_info *opinfo = opinfo_get(fp);

@@ -1849,6 +1850,12 @@ int smb2_check_durable_oplock(struct ksmbd_conn *conn,
 	if (!opinfo)
 		return 0;
 
+	if (ksmbd_vfs_compare_durable_owner(fp, user) == false) {
+		ksmbd_debug(SMB, "Durable handle reconnect failed: owner mismatch\n");
+		ret = -EBADF;
+		goto out;
+	}
+
 	if (opinfo->is_lease == false) {
 		if (lctx) {
 			pr_err("create context include lease\n");
fs/smb/server/oplock.h +1 -0
index 921e3199e4df..d91a8266e065 100644
@@ -126,5 +126,6 @@ int smb2_check_durable_oplock(struct ksmbd_conn *conn,
 			      struct ksmbd_share_config *share,
 			      struct ksmbd_file *fp,
 			      struct lease_ctx_info *lctx,
+			      struct ksmbd_user *user,
 			      char *name);
 #endif /* __KSMBD_OPLOCK_H */
fs/smb/server/smb2pdu.c +2 -1
index 764a78dec46a..d0b05878757e 100644
@@ -3013,7 +3013,8 @@ int smb2_open(struct ksmbd_work *work)
 		}
 
 		if (dh_info.reconnected == true) {
-			rc = smb2_check_durable_oplock(conn, share, dh_info.fp, lc, name);
+			rc = smb2_check_durable_oplock(conn, share, dh_info.fp,
+					lc, sess->user, name);
 			if (rc) {
 				ksmbd_put_durable_fd(dh_info.fp);
 				goto err_out2;
fs/smb/server/vfs_cache.c +78 -9

161 lines not on this page · raw message

fs/smb/server/vfs_cache.h +11 -1
index 78b506c5ef03..866f32c10d4d 100644
@@ -68,6 +68,13 @@ enum {
 	FP_CLOSED
 };
 
+/* Owner information for durable handle reconnect */
+struct durable_owner {
+	unsigned int uid;
+	unsigned int gid;
+	char *name;
+};
+
 struct ksmbd_file {
 	struct file			*filp;
 	u64				persistent_id;

@@ -114,6 +121,7 @@ struct ksmbd_file {
 	bool				is_resilient;
 
 	bool                            is_posix_ctxt;
+	struct durable_owner		owner;
 };
 
 static inline void set_ctx_actor(struct dir_context *ctx,

@@ -140,7 +148,7 @@ static inline bool ksmbd_stream_fd(struct ksmbd_file *fp)
 }
 
 int ksmbd_init_file_table(struct ksmbd_file_table *ft);
-void ksmbd_destroy_file_table(struct ksmbd_file_table *ft);
+void ksmbd_destroy_file_table(struct ksmbd_session *sess);
 int ksmbd_close_fd(struct ksmbd_work *work, u64 id);
 struct ksmbd_file *ksmbd_lookup_fd_fast(struct ksmbd_work *work, u64 id);
 struct ksmbd_file *ksmbd_lookup_foreign_fd(struct ksmbd_work *work, u64 id);

@@ -166,6 +174,8 @@ void ksmbd_free_global_file_table(void);
 void ksmbd_set_fd_limit(unsigned long limit);
 void ksmbd_update_fstate(struct ksmbd_file_table *ft, struct ksmbd_file *fp,
 			 unsigned int state);
+bool ksmbd_vfs_compare_durable_owner(struct ksmbd_file *fp,
+		struct ksmbd_user *user);
 
 /*
  * INODE hash
maintainer
#1 lore raw

PATCH 1/1 ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger

From: Namjae Jeon <[email protected]>

[ Upstream commit 235e32320a470fcd3998fb3774f2290a0eb302a1 ]

When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list.

Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did:

    spin_lock(&fp->conn->llist_lock);

This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect().

The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out.

To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths:
- Safely skip clist deletion when list is empty and fp->conn is NULL.
- Remove the lock from the old connection's lock_list in session_fd_check()
- Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().

Fixes c8efcc786146 ("ksmbd: add support for durable handles v1/v2")
Co-developed-by munan Huang <[email protected]>
Signed-off-by munan Huang <[email protected]>
Reviewed-by ChenXiaoSong <[email protected]>
Signed-off-by Namjae Jeon <[email protected]>
Signed-off-by Steve French <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
---
 fs/smb/server/vfs_cache.c | 41 ++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)
fs/smb/server/vfs_cache.c +30 -11
index 6ef116585af64..08f25a2d75416 100644
@@ -370,9 +370,11 @@ static void __ksmbd_close_fd(struct ksmbd_file_table *ft, struct ksmbd_file *fp)
 	 * there are not accesses to fp->lock_list.
 	 */
 	list_for_each_entry_safe(smb_lock, tmp_lock, &fp->lock_list, flist) {
-		spin_lock(&fp->conn->llist_lock);
-		list_del(&smb_lock->clist);
-		spin_unlock(&fp->conn->llist_lock);
+		if (!list_empty(&smb_lock->clist) && fp->conn) {
+			spin_lock(&fp->conn->llist_lock);
+			list_del(&smb_lock->clist);
+			spin_unlock(&fp->conn->llist_lock);
+		}
 
 		list_del(&smb_lock->flist);
 		locks_free_lock(smb_lock->fl);

@@ -902,6 +904,7 @@ static bool session_fd_check(struct ksmbd_tree_connect *tcon,
 	struct ksmbd_inode *ci;
 	struct oplock_info *op;
 	struct ksmbd_conn *conn;
+	struct ksmbd_lock *smb_lock, *tmp_lock;
 
 	if (!is_reconnectable(fp))
 		return false;

@@ -918,6 +921,12 @@ static bool session_fd_check(struct ksmbd_tree_connect *tcon,
 	}
 	up_write(&ci->m_lock);
 
+	list_for_each_entry_safe(smb_lock, tmp_lock, &fp->lock_list, flist) {
+		spin_lock(&fp->conn->llist_lock);
+		list_del_init(&smb_lock->clist);
+		spin_unlock(&fp->conn->llist_lock);
+	}
+
 	fp->conn = NULL;
 	fp->tcon = NULL;
 	fp->volatile_id = KSMBD_NO_FID;

@@ -996,6 +1005,9 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp)
 {
 	struct ksmbd_inode *ci;
 	struct oplock_info *op;
+	struct ksmbd_conn *conn = work->conn;
+	struct ksmbd_lock *smb_lock;
+	unsigned int old_f_state;
 
 	if (!fp->is_durable || fp->conn || fp->tcon) {
 		pr_err("Invalid durable fd [%p:%p]\n", fp->conn, fp->tcon);

@@ -1007,9 +1019,23 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp)
 		return -EBADF;
 	}
 
-	fp->conn = work->conn;
+	old_f_state = fp->f_state;
+	fp->f_state = FP_NEW;
+	__open_id(&work->sess->file_table, fp, OPEN_ID_TYPE_VOLATILE_ID);
+	if (!has_file_id(fp->volatile_id)) {
+		fp->f_state = old_f_state;
+		return -EBADF;
+	}
+
+	fp->conn = conn;
 	fp->tcon = work->tcon;
 
+	list_for_each_entry(smb_lock, &fp->lock_list, flist) {
+		spin_lock(&conn->llist_lock);
+		list_add_tail(&smb_lock->clist, &conn->lock_list);
+		spin_unlock(&conn->llist_lock);
+	}
+
 	ci = fp->f_ci;
 	down_write(&ci->m_lock);
 	list_for_each_entry_rcu(op, &ci->m_op_list, op_entry) {

@@ -1020,13 +1046,6 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp)
 	}
 	up_write(&ci->m_lock);
 
-	fp->f_state = FP_NEW;
-	__open_id(&work->sess->file_table, fp, OPEN_ID_TYPE_VOLATILE_ID);
-	if (!has_file_id(fp->volatile_id)) {
-		fp->conn = NULL;
-		fp->tcon = NULL;
-		return -EBADF;
-	}
 	return 0;
 }
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