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 56CDD4534B4; Tue, 16 Jun 2026 16:00:29 +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=1781625630; cv=none; b=lYU36sxd+QPqRCASPIPg24IZUj729LBq5Iu7TY3szWNApTHv88SKaBRc6OqXx46APPHDvzAucb7aye3m6XPzdogX2saOHCipZNBn0ZOUZ+i8WnbJPySL5dqEeqGs/t/PkuvyGmxzXjcUMAtePywI/+slvQE1Mq6GjgQPbh/gv/I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781625630; c=relaxed/simple; bh=AbfSACgVlAvItdRWyYhPlnkcqGelrFOBd6vRC0jVDT0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cQZbE/nUQ5ueRsJeTJQAEMmc+MkIvbvid56ZupcLxvh1FXcfr5OP4pdomFIUamK58L9Eb7nJP1SqJ1+pRt0lCZaOBRBrsES5dutk4X8JCbThW6KI5n18u4xWjVNYQ/uUzyM9UayIT/gRXR2cc3WRm/U0yPa+XElKkbEtRwCrJ0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qi5pAC44; 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="qi5pAC44" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 633371F000E9; Tue, 16 Jun 2026 16:00:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781625629; bh=OPas+cDFqBZR6D037aHvtGc/dkJeM3Ji4B18mqWxYwI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qi5pAC44jWasGLfqzz5T2uIOCxPSjrup26lkpPbvTe9Ls+N/MeabxkwnYhjWk86i9 QsPFh/Qs1T0uhDLWjRy9ouBCFreN3FN6KRQQC1LcIiZ9Y/xprQ3M2r9Ino1XtH0YKO +ub5vfFTmYiL6ZqVjQKKop7SqH22vgxw8caw6Va8= 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 6.18 170/325] ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL Date: Tue, 16 Jun 2026 20:29:26 +0530 Message-ID: <20260616145106.300754133@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145057.827196531@linuxfoundation.org> References: <20260616145057.827196531@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gil Portnoy commit f580d27e8928828693df44ba2db0fffdbe11dfea upstream. A deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on conn->async_requests via setup_async_work(), with cancel_fn = smb2_remove_blocked_lock and cancel_argv[0] pointing at the struct file_lock. When the request is cancelled, the worker frees the file_lock with locks_free_lock() and takes the cancelled early-exit, which "goto out"s and never reaches release_async_work() -- the only site that unlinks the work from conn->async_requests and clears cancel_fn/cancel_argv. The work therefore stays matchable on async_requests with a live cancel_fn pointing at the freed file_lock, until connection teardown finally runs release_async_work(). smb2_cancel() fires cancel_fn unconditionally with no state guard, so a second SMB2_CANCEL for the same AsyncId, arriving in that window, re-runs smb2_remove_blocked_lock() on the freed file_lock -- a slab use-after-free: 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 (cancelled branch) ... cache file_lock_cache of size 192 Reproduced on mainline with KASAN by an authenticated SMB client. Skip a work whose state is already KSMBD_WORK_CANCELLED so its cancel callback cannot be fired a second time. 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 | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -7328,6 +7328,17 @@ int smb2_cancel(struct ksmbd_work *work) le64_to_cpu(hdr->Id.AsyncId)) 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. + */ + if (iter->state == KSMBD_WORK_CANCELLED) + break; + ksmbd_debug(SMB, "smb2 with AsyncId %llu cancelled command = 0x%x\n", le64_to_cpu(hdr->Id.AsyncId),