FAILED: patch "[PATCH] ksmbd: fix memory leaks and NULL deref in smb2_lock()" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 309b44ed684496ed3f9c5715d10b899338623512
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026032951-delivery-lilly-753c@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 309b44ed684496ed3f9c5715d10b899338623512 Mon Sep 17 00:00:00 2001
From: Werner Kasselman <[email protected]>
Date: Tue, 17 Mar 2026 07:55:37 +0000
Subject: [PATCH] ksmbd: fix memory leaks and NULL deref in smb2_lock()

smb2_lock() has three error handling issues after list_del() detaches smb_lock from lock_list at no_check_cl:

1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK path, goto out leaks smb_lock and its flock because the out:
handler only iterates lock_list and rollback_list, neither of which contains the detached smb_lock.

2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out leaks smb_lock and flock for the same reason. The error code returned to the dispatcher is also stale.

3) In the rollback path, smb_flock_init() can return NULL on allocation failure. The result is dereferenced unconditionally, causing a kernel NULL pointer dereference. Add a NULL check to prevent the crash and clean up the bookkeeping; the VFS lock itself cannot be rolled back without the allocation and will be released at file or connection teardown.

Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before the if(!rc) check in the UNLOCK branch so all exit paths share one free site, and by freeing smb_lock and flock before goto out in the non-UNLOCK branch. Propagate the correct error code in both cases. Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding a NULL check for locks_free_lock(rlock) in the shared cleanup.

Found via call-graph analysis using sqry.

index 8fa780e8efd0..24f8d58493d0 100644
@@ -7592,14 +7592,15 @@ int smb2_lock(struct ksmbd_work *work)
 		rc = vfs_lock_file(filp, smb_lock->cmd, flock, NULL);
 skip:
 		if (smb_lock->flags & SMB2_LOCKFLAG_UNLOCK) {
+			locks_free_lock(flock);
+			kfree(smb_lock);
 			if (!rc) {
 				ksmbd_debug(SMB, "File unlocked\n");
 			} else if (rc == -ENOENT) {
 				rsp->hdr.Status = STATUS_NOT_LOCKED;
+				err = rc;
 				goto out;
 			}
-			locks_free_lock(flock);
-			kfree(smb_lock);
 		} else {
 			if (rc == FILE_LOCK_DEFERRED) {
 				void **argv;

@@ -7668,6 +7669,9 @@ int smb2_lock(struct ksmbd_work *work)
 				spin_unlock(&work->conn->llist_lock);
 				ksmbd_debug(SMB, "successful in taking lock\n");
 			} else {
+				locks_free_lock(flock);
+				kfree(smb_lock);
+				err = rc;
 				goto out;
 			}
 		}

@@ -7698,13 +7702,17 @@ int smb2_lock(struct ksmbd_work *work)
 		struct file_lock *rlock = NULL;
 
 		rlock = smb_flock_init(filp);
-		rlock->c.flc_type = F_UNLCK;
-		rlock->fl_start = smb_lock->start;
-		rlock->fl_end = smb_lock->end;
+		if (rlock) {
+			rlock->c.flc_type = F_UNLCK;
+			rlock->fl_start = smb_lock->start;
+			rlock->fl_end = smb_lock->end;
 
-		rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
-		if (rc)
-			pr_err("rollback unlock fail : %d\n", rc);
+			rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
+			if (rc)
+				pr_err("rollback unlock fail : %d\n", rc);
+		} else {
+			pr_err("rollback unlock alloc failed\n");
+		}
 
 		list_del(&smb_lock->llist);
 		spin_lock(&work->conn->llist_lock);

@@ -7714,7 +7722,8 @@ int smb2_lock(struct ksmbd_work *work)
 		spin_unlock(&work->conn->llist_lock);
 
 		locks_free_lock(smb_lock->fl);
-		locks_free_lock(rlock);
+		if (rlock)
+			locks_free_lock(rlock);
 		kfree(smb_lock);
 	}
 out2:

From: Werner Kasselman <[email protected]>

[ Upstream commit 309b44ed684496ed3f9c5715d10b899338623512 ]

smb2_lock() has three error handling issues after list_del() detaches smb_lock from lock_list at no_check_cl:

1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK path, goto out leaks smb_lock and its flock because the out:
handler only iterates lock_list and rollback_list, neither of which contains the detached smb_lock.

2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out leaks smb_lock and flock for the same reason. The error code returned to the dispatcher is also stale.

3) In the rollback path, smb_flock_init() can return NULL on allocation failure. The result is dereferenced unconditionally, causing a kernel NULL pointer dereference. Add a NULL check to prevent the crash and clean up the bookkeeping; the VFS lock itself cannot be rolled back without the allocation and will be released at file or connection teardown.

Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before the if(!rc) check in the UNLOCK branch so all exit paths share one free site, and by freeing smb_lock and flock before goto out in the non-UNLOCK branch. Propagate the correct error code in both cases. Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding a NULL check for locks_free_lock(rlock) in the shared cleanup.

Found via call-graph analysis using sqry.

---
 fs/smb/server/smb2pdu.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

index bdd2214c79f98..ca59badb42a73 100644
@@ -7515,14 +7515,15 @@ int smb2_lock(struct ksmbd_work *work)
 		rc = vfs_lock_file(filp, smb_lock->cmd, flock, NULL);
 skip:
 		if (smb_lock->flags & SMB2_LOCKFLAG_UNLOCK) {
+			locks_free_lock(flock);
+			kfree(smb_lock);
 			if (!rc) {
 				ksmbd_debug(SMB, "File unlocked\n");
 			} else if (rc == -ENOENT) {
 				rsp->hdr.Status = STATUS_NOT_LOCKED;
+				err = rc;
 				goto out;
 			}
-			locks_free_lock(flock);
-			kfree(smb_lock);
 		} else {
 			if (rc == FILE_LOCK_DEFERRED) {
 				void **argv;

@@ -7591,6 +7592,9 @@ int smb2_lock(struct ksmbd_work *work)
 				spin_unlock(&work->conn->llist_lock);
 				ksmbd_debug(SMB, "successful in taking lock\n");
 			} else {
+				locks_free_lock(flock);
+				kfree(smb_lock);
+				err = rc;
 				goto out;
 			}
 		}

@@ -7621,13 +7625,17 @@ int smb2_lock(struct ksmbd_work *work)
 		struct file_lock *rlock = NULL;
 
 		rlock = smb_flock_init(filp);
-		rlock->fl_type = F_UNLCK;
-		rlock->fl_start = smb_lock->start;
-		rlock->fl_end = smb_lock->end;
+		if (rlock) {
+			rlock->fl_type = F_UNLCK;
+			rlock->fl_start = smb_lock->start;
+			rlock->fl_end = smb_lock->end;
 
-		rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
-		if (rc)
-			pr_err("rollback unlock fail : %d\n", rc);
+			rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
+			if (rc)
+				pr_err("rollback unlock fail : %d\n", rc);
+		} else {
+			pr_err("rollback unlock alloc failed\n");
+		}
 
 		list_del(&smb_lock->llist);
 		spin_lock(&work->conn->llist_lock);

@@ -7637,7 +7645,8 @@ int smb2_lock(struct ksmbd_work *work)
 		spin_unlock(&work->conn->llist_lock);
 
 		locks_free_lock(smb_lock->fl);
-		locks_free_lock(rlock);
+		if (rlock)
+			locks_free_lock(rlock);
 		kfree(smb_lock);
 	}
 out2:

2.53.0