From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793701325; b=xyYwt58gi9c0RYsE0eN86WoLFr1URHlv65j6UTtsYiXRMo8dO9UDnvSnq611+caHJ/7Q 7fCKE9zG1IRNVbdwPjHTga99RilH+P55NqgVJ07V875LB4bhSkIAqv+Bh3cCFvpmjmC+p S1vX+TC7la6UpCPhois3o08nk/Pe2HRPqIAKS8BP5qUvBfQ0M19g/eVcj2h+XTI3CwElT tuy7Du3fEcZQo7bMT3vWxA8Oq68sKZW6AyEmoiR0b+vblWUVCk6YlMa23HGyZJhRLx+Hn EmkjqeX0OOYo8hPBQeYXSJZ2WE/u5TmiEmtT+c/zVm2GRqW2aQX60Gfwc/P8YNELbNQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793701325; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=D/HH+exENazI4u5+MCyuurZyQgpyCj5hNnQJJViSzNc=; b=ORtE7lduPuCCpCv/O7ObLupDuC2UmebLaCoIjLENHigQCpcentlvw4VxE8pXDrVm98IS JIaVFWkzRvV8G1+b2KyzPkR+aUqWQdCr5mRDKUEX/+lBBs4oHVQIJB+D5l1wQ3Bp+SKNV Fg1dvOKIyrXMBer0MiI/X0/qxPRWDa36RvYvs1iC89BP7N6+7en+Db6N+R6QmYgPoJqzz pQ+VXfwqVVxUV2JzhQX7gai470HC7JTfmiJcAVM8ngQHsGtLZ7Bk+Kgur5b5w0CyS2Fa9 5YXMwoetIdlG/+U8I0hCBWnvbRlEHAxT5NnI+PWNkRC+23XqjFRAd85cM2nEAekCbuQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=EQb9lSX5; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 29822606D83D for ; Tue, 3 Nov 2026 10:22:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=EQb9lSX5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6AE51F00A15; Tue, 3 Nov 2026 10:22:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793701325; bh=D/HH+exENazI4u5+MCyuurZyQgpyCj5hNnQJJViSzNc=; h=Subject:To:Cc:From:Date; b=EQb9lSX5MK2jCMAc5+fOI80COlGj9DhOLIiwXFv2eSyAEDmO18qsmTBOvUXuXlm1p eGKBjZBjlQVT2cnrP+uugg0WYCoY+NpLrfYVuAwA995KiU+flTLeAaALS2M5O5MaKa zyU1wJWXjEJLXXRH/cNxgfZWOidwSSCoe8cfBBlw= Subject: FAILED: patch "[PATCH] ksmbd: fix use-after-free after a failed durable reconnect" failed to apply to 6.18-stable tree To: icb@fastmail.org,linkinjeon@kernel.org Cc: From: Date: Tue, 03 Nov 2026 11:21:50 +0100 Message-ID: <2026110350-subplot-mounted-fdcb@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-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 . 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-6.18.y git checkout FETCH_HEAD git cherry-pick -x 248b5819591c577727930e4e255a455235fab50a # git commit -s git send-email --to '' --in-reply-to '2026110350-subplot-mounted-fdcb@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 248b5819591c577727930e4e255a455235fab50a Mon Sep 17 00:00:00 2001 From: Ian Bridges Date: Tue, 27 Oct 2026 10:25:19 -0500 Subject: [PATCH] ksmbd: fix use-after-free after a failed durable reconnect ksmbd_reopen_durable_fd() republishes a detached durable handle in the reconnecting session's file table and takes no reference for that entry. If smb2_open() then fails, cleanup relies on the final ksmbd_fd_put() to remove the volatile id. Two reconnects of the same handle can both take a lookup reference before either attaches it. If the one that reopens first then fails and drops its references first, the other request makes the final put through ksmbd_put_durable_fd(). That frees the handle without removing the first session's table entry, so tearing that session down writes to freed memory. BUG: KASAN: slab-use-after-free in __close_file_table_ids+0x14d/0x740 [ksmbd] Call Trace: __close_file_table_ids+0x14d/0x740 [ksmbd] ksmbd_destroy_file_table+0x76/0x100 [ksmbd] ksmbd_session_destroy+0xf8/0x480 [ksmbd] ksmbd_dispose_sessions+0x13e/0x200 [ksmbd] ksmbd_conn_sessions_cleanup+0x4c3/0x6d0 [ksmbd] Freed by task 1030: __ksmbd_close_fd+0x97d/0x1000 [ksmbd] smb2_open+0x14eb/0xd9f0 [ksmbd] Commit 3515503322f4 ("ksmbd: fix durable reconnect error path file lifetime") handles a final put made by the reconnecting request, but not one made by another holder. Remove the volatile id under the file-table lock on this error path, before the references are dropped, as ksmbd_close_fd() does on the request_open path just above. Removal then no longer depends on which holder makes the final put. The stale comment in the reconnect cleanup is updated to match. A successful reconnect is unchanged. Fixes: c8efcc786146 ("ksmbd: add support for durable handles v1/v2") Cc: stable@vger.kernel.org Signed-off-by: Ian Bridges Signed-off-by: Namjae Jeon diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index b306bc6e21ee..4dc91d4f1a94 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -5628,6 +5628,8 @@ int smb2_open(struct ksmbd_work *work) ksmbd_close_fd(work, fp->volatile_id); smb2_complete_request_open(work); } else { + if (dh_info.reconnected && fp == dh_info.fp) + ksmbd_unpublish_reopened_fd(work, fp); ksmbd_fd_put(work, fp); } } @@ -5641,10 +5643,9 @@ int smb2_open(struct ksmbd_work *work) if (dh_info.reconnected) { /* * If reconnect succeeded, fp was republished in the - * session file table. On a later error, ksmbd_fd_put() - * above drops the session reference; drop the durable - * lookup reference through the same session-aware path so - * final close removes the volatile id before freeing fp. + * session file table, and the error path above has + * already removed its volatile id. Drop the durable + * lookup reference through the same session-aware path. */ if (rc && fp == dh_info.fp) ksmbd_fd_put(work, dh_info.fp); diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c index 4368e069fd5e..f9079c529d07 100644 --- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -1074,6 +1074,34 @@ void ksmbd_wake_session_blocked_works(struct ksmbd_session *sess) read_unlock(&ft->lock); } +/** + * ksmbd_unpublish_reopened_fd() - remove a reopened durable handle from the + * session file table after its CREATE failed + * @work: smb work of the failed CREATE + * @fp: durable handle republished by ksmbd_reopen_durable_fd() + * + * The reopen publishes @fp in this session's table without taking a reference + * for the entry, so the CREATE error path's puts need not be the last ones. + * Another holder of a global-table reference, such as a concurrent reconnect + * of the same handle, can drop the last one through ksmbd_put_durable_fd(), + * which frees @fp without touching this table. Remove the id here, while + * the caller still holds its references. + * + * Every path that removes the id before the final put also clears + * @fp->volatile_id under ft->lock, so a valid id is still @fp's entry. + */ +void ksmbd_unpublish_reopened_fd(struct ksmbd_work *work, struct ksmbd_file *fp) +{ + struct ksmbd_file_table *ft = &work->sess->file_table; + + write_lock(&ft->lock); + if (has_file_id(fp->volatile_id)) { + idr_remove(ft->idr, fp->volatile_id); + fp->volatile_id = KSMBD_NO_FID; + } + write_unlock(&ft->lock); +} + int ksmbd_close_fd(struct ksmbd_work *work, u64 id) { struct ksmbd_file *fp; diff --git a/fs/smb/server/vfs_cache.h b/fs/smb/server/vfs_cache.h index c00d92fdf94a..a0239ec178d8 100644 --- a/fs/smb/server/vfs_cache.h +++ b/fs/smb/server/vfs_cache.h @@ -205,6 +205,8 @@ 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_session *sess); int ksmbd_close_fd(struct ksmbd_work *work, u64 id); +void ksmbd_unpublish_reopened_fd(struct ksmbd_work *work, + struct ksmbd_file *fp); 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); struct ksmbd_file *ksmbd_lookup_fd_slow(struct ksmbd_work *work, u64 id,