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; }