From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 18D2A43C7C5; Tue, 21 Jul 2026 21:11:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784668278; cv=none; b=j1dTUT5k39RtCx9sY1G9s5f7ZrF6M0QLl1QWgUCcFviNL1VPoDXpiUWw26VbPluu7wS3gel7BjiC2uO36qCu64r1+5X8ZSBKo3QwJP+uaaJk+t06NzPqidZpYDnSJ56fWzzvljrIL0bo5dpLFc5nXpQBeJ4O84TEEgIHhVQhinA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784668278; c=relaxed/simple; bh=1uBYIS2J/ltckugyt+AJF0gUWRSWqkBZyd94cr0pLTY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OQIK+MoHE2GzRcjgZZUffKmgWYjRV0U1drFOb9FFNYT1i00WXvxqkmjB56L95LPfISaONQyhDTvd+08749StRfXosVZ6AqyA6JEkTTW2FU5X0Mla+Uz73hoO68Ktns5y7s9Xe9We/ypsftUslFO3foGSDczIhI7YR0rug5SJv8c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OiFJ6ANw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="OiFJ6ANw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D49D1F000E9; Tue, 21 Jul 2026 21:11:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784668277; bh=96aCNj3aGNt4gZXjU09X8c7thzGo91GtJVvmhMegsfk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=OiFJ6ANwFE4YjhuXgZYqJra38Q7z0GPU9TWeT63ntEX1LddQASbyno9zHtqWc4jk/ xLU9QjKemIuPDS6TUpMODSalrRKahrKDXuyZOioqOR/uuTlpUEwSir9qEXnwVQZp/S tO3c8ypBZmL35GhEpMDqW1Os6g0jrVy+xaJvSU1A= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gil Portnoy , Namjae Jeon , Steve French Subject: [PATCH 6.1 0116/1067] ksmbd: fix use-after-free of a deferred file_lock on SMB2_CLOSE then SMB2_CANCEL Date: Tue, 21 Jul 2026 17:11:57 +0200 Message-ID: <20260721152427.183368590@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152424.521567757@linuxfoundation.org> References: <20260721152424.521567757@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gil Portnoy commit 10f293a07f9e10e988b0ae44e2e99c631f5a68e0 upstream. Commit f580d27e8928 ("ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL") made smb2_cancel() skip a work whose state is KSMBD_WORK_CANCELLED, so its cancel_fn cannot be fired a second time. But KSMBD_WORK has three states (ACTIVE, CANCELLED, CLOSED), and the same freeing producer path is reached for CLOSED too: SMB2_CLOSE on the locking handle -> set_close_state_blocked_works() sets the deferred work's state to KSMBD_WORK_CLOSED and wakes the smb2_lock() worker. The worker takes the non-ACTIVE early-exit, locks_free_lock()s the file_lock and, because the state is not KSMBD_WORK_CANCELLED, takes the STATUS_RANGE_NOT_LOCKED branch with "goto out2" -- which, like the cancelled branch, skips release_async_work(). The work stays on conn->async_requests with a live cancel_fn = smb2_remove_blocked_lock pointing at the freed file_lock. A subsequent SMB2_CANCEL for the same AsyncId then passes the KSMBD_WORK_CANCELLED-only guard (its state is KSMBD_WORK_CLOSED), so smb2_cancel() fires cancel_fn again over the freed file_lock -- the same use-after-free fixed, via SMB2_CLOSE instead of a first SMB2_CANCEL: BUG: KASAN: slab-use-after-free in __locks_delete_block __locks_delete_block locks_delete_block ksmbd_vfs_posix_lock_unblock smb2_remove_blocked_lock smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn handle_ksmbd_work Allocated by ...: locks_alloc_lock <- smb2_lock Freed by ...: locks_free_lock <- smb2_lock (non-ACTIVE early-exit) ... cache file_lock_cache of size 192 Reproduced on mainline 7.1-rc7 (which already contains f580d27e8928) with KASAN by an authenticated SMB client; the double-SMB2_CANCEL control is silent on that kernel, so the splat is attributable to the CLOSE trigger. Only an ACTIVE deferred work may have its cancel_fn fired: both terminal states (CANCELLED and CLOSED) reach the smb2_lock() early-exit that frees the file_lock and skips release_async_work(). Guard on KSMBD_WORK_ACTIVE so any non-active work is skipped. Fixes: f580d27e8928 ("ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL") Cc: stable@vger.kernel.org Signed-off-by: Gil Portnoy Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smb2pdu.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -6816,14 +6816,14 @@ int smb2_cancel(struct ksmbd_work *work) continue; /* - * A cancelled deferred byte-range lock frees its - * file_lock and takes the smb2_lock() early-exit that - * skips release_async_work(), so the work stays on - * conn->async_requests with a live cancel_fn pointing - * at the freed file_lock. Re-firing it on a second - * SMB2_CANCEL is a use-after-free. + * Only an ACTIVE deferred work may have its cancel_fn + * fired. A CANCELLED or CLOSED work already took the + * smb2_lock() non-ACTIVE early-exit that frees the + * file_lock and skips release_async_work(), so it is + * still on conn->async_requests with a live cancel_fn + * pointing at the freed file_lock. */ - if (iter->state == KSMBD_WORK_CANCELLED) + if (iter->state != KSMBD_WORK_ACTIVE) break; ksmbd_debug(SMB,