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FAILED: patch "[PATCH] smb: client: fix potential UAF in smb2_close_cached_fid()" failed to apply to 6.1-stable tree

PATCH [email protected] 1 participant 1 message Nov 9, 2025

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Stable branch SMB client (CIFS)
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The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 734e99623c5b65bf2c03e35978a0b980ebc3c2f8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025110956-pork-relearn-9e1e@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 734e99623c5b65bf2c03e35978a0b980ebc3c2f8 Mon Sep 17 00:00:00 2001
From: Henrique Carvalho <[email protected]>
Date: Mon, 3 Nov 2025 19:52:55 -0300
Subject: [PATCH] smb: client: fix potential UAF in smb2_close_cached_fid()

find_or_create_cached_dir() could grab a new reference after kref_put() had seen the refcount drop to zero but before cfid_list_lock is acquired in smb2_close_cached_fid(), leading to use-after-free.

Switch to kref_put_lock() so cfid_release() is called with cfid_list_lock held, closing that gap.

Fixes ebe98f1447bb ("cifs: enable caching of directories for which a lease is held")
Cc [email protected]
Reported-by Jay Shin <[email protected]>
Reviewed-by Paulo Alcantara (Red Hat) <[email protected]>
Signed-off-by Henrique Carvalho <[email protected]>
Signed-off-by Steve French <[email protected]>
fs/smb/client/cached_dir.c +9 -7
index b8ac7b7faf61..018055fd2cdb 100644
@@ -388,11 +388,11 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 			 * lease. Release one here, and the second below.
 			 */
 			cfid->has_lease = false;
-			kref_put(&cfid->refcount, smb2_close_cached_fid);
+			close_cached_dir(cfid);
 		}
 		spin_unlock(&cfids->cfid_list_lock);
 
-		kref_put(&cfid->refcount, smb2_close_cached_fid);
+		close_cached_dir(cfid);
 	} else {
 		*ret_cfid = cfid;
 		atomic_inc(&tcon->num_remote_opens);

@@ -438,12 +438,14 @@ int open_cached_dir_by_dentry(struct cifs_tcon *tcon,
 
 static void
 smb2_close_cached_fid(struct kref *ref)
+__releases(&cfid->cfids->cfid_list_lock)
 {
 	struct cached_fid *cfid = container_of(ref, struct cached_fid,
 					       refcount);
 	int rc;
 
-	spin_lock(&cfid->cfids->cfid_list_lock);
+	lockdep_assert_held(&cfid->cfids->cfid_list_lock);
+
 	if (cfid->on_list) {
 		list_del(&cfid->entry);
 		cfid->on_list = false;

@@ -478,7 +480,7 @@ void drop_cached_dir_by_name(const unsigned int xid, struct cifs_tcon *tcon,
 	spin_lock(&cfid->cfids->cfid_list_lock);
 	if (cfid->has_lease) {
 		cfid->has_lease = false;
-		kref_put(&cfid->refcount, smb2_close_cached_fid);
+		close_cached_dir(cfid);
 	}
 	spin_unlock(&cfid->cfids->cfid_list_lock);
 	close_cached_dir(cfid);

@@ -487,7 +489,7 @@ void drop_cached_dir_by_name(const unsigned int xid, struct cifs_tcon *tcon,
 
 void close_cached_dir(struct cached_fid *cfid)
 {
-	kref_put(&cfid->refcount, smb2_close_cached_fid);
+	kref_put_lock(&cfid->refcount, smb2_close_cached_fid, &cfid->cfids->cfid_list_lock);
 }
 
 /*

@@ -596,7 +598,7 @@ cached_dir_offload_close(struct work_struct *work)
 
 	WARN_ON(cfid->on_list);
 
-	kref_put(&cfid->refcount, smb2_close_cached_fid);
+	close_cached_dir(cfid);
 	cifs_put_tcon(tcon, netfs_trace_tcon_ref_put_cached_close);
 }
 

@@ -762,7 +764,7 @@ static void cfids_laundromat_worker(struct work_struct *work)
 			 * Drop the ref-count from above, either the lease-ref (if there
 			 * was one) or the extra one acquired.
 			 */
-			kref_put(&cfid->refcount, smb2_close_cached_fid);
+			close_cached_dir(cfid);
 	}
 	queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
 			   dir_cache_timeout * HZ);