FAILED: patch "[PATCH] ksmbd: Fix UAF in __close_file_table_ids" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org>.

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 36991c1ccde2d5a521577c448ffe07fcccfe104d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025050939-activism-hesitant-7576@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 36991c1ccde2d5a521577c448ffe07fcccfe104d Mon Sep 17 00:00:00 2001
From: Sean Heelan <seanheelan@gmail.com>
Date: Tue, 6 May 2025 22:04:52 +0900
Subject: [PATCH] ksmbd: Fix UAF in __close_file_table_ids

A use-after-free is possible if one thread destroys the file
via __ksmbd_close_fd while another thread holds a reference to
it. The existing checks on fp->refcount are not sufficient to
prevent this.

The fix takes ft->lock around the section which removes the
file from the file table. This prevents two threads acquiring the
same file pointer via __close_file_table_ids, as well as the other
functions which retrieve a file from the IDR and which already use
this same lock.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Heelan <seanheelan@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c
index 1f8fa3468173..dfed6fce8904 100644
--- a/fs/smb/server/vfs_cache.c
+++ b/fs/smb/server/vfs_cache.c
@@ -661,21 +661,40 @@ __close_file_table_ids(struct ksmbd_file_table *ft,
 		       bool (*skip)(struct ksmbd_tree_connect *tcon,
 				    struct ksmbd_file *fp))
 {
-	unsigned int			id;
-	struct ksmbd_file		*fp;
-	int				num = 0;
+	struct ksmbd_file *fp;
+	unsigned int id = 0;
+	int num = 0;
 
-	idr_for_each_entry(ft->idr, fp, id) {
-		if (skip(tcon, fp))
+	while (1) {
+		write_lock(&ft->lock);
+		fp = idr_get_next(ft->idr, &id);
+		if (!fp) {
+			write_unlock(&ft->lock);
+			break;
+		}
+
+		if (skip(tcon, fp) ||
+		    !atomic_dec_and_test(&fp->refcount)) {
+			id++;
+			write_unlock(&ft->lock);
 			continue;
+		}
 
 		set_close_state_blocked_works(fp);
+		idr_remove(ft->idr, fp->volatile_id);
+		fp->volatile_id = KSMBD_NO_FID;
+		write_unlock(&ft->lock);
+
+		down_write(&fp->f_ci->m_lock);
+		list_del_init(&fp->node);
+		up_write(&fp->f_ci->m_lock);
 
-		if (!atomic_dec_and_test(&fp->refcount))
-			continue;
 		__ksmbd_close_fd(ft, fp);
+
 		num++;
+		id++;
 	}
+
 	return num;
 }