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 CFD7F3F822B; Thu, 16 Jul 2026 14:06:05 +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=1784210766; cv=none; b=UjJn+PNtzSgd+KjsXn4FCHwdZeQ95FOJlOhq9YmbhOHZlkwXrh9G3Cgnh2qCjXM+y3bt4zv+C6OWAk17v7JjJWVS9StlMRw6mMPyIztXMoipYYGbNz3gBRVKG1RdjJxri2mUUsJolOGwQN3HDJkVNawLsdAT+Jo1OREKYrQbLwM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210766; c=relaxed/simple; bh=neGrDEl2twTZJ0PGZxzvIRZbUtPuX/xcAoxdj0rVB2U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p5WXbrT4GJhJ08eKJpozVGX3zulVXDt1szABuf4YrqlrhOPFGToBFmQQ/IA1xEZT5tz84XyF75KrYgZBKFEw0XP9xBLh6U3gmhC9iKH1fSBA37hiFaGtSO97AN8qGfK4slBlLMZEcs4D0tmQzb0HaFs+9VTtJqefhenkEOJjv4E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cKp6Qcc8; 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="cKp6Qcc8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40D021F00A3A; Thu, 16 Jul 2026 14:06:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784210765; bh=oWa6G/LnmWlmk8TIVt/nxBtoOaOv0Uz9JgCoLkXBeHw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cKp6Qcc8zVdFrBk9UmTUtVyrGt30aQ7WytBJYbPcF1jO6R1AroI0YXvQXFGNBu3Kg MkptDD5Dv08Ek9ONXCY77FDl4LVpGmaWDjla/7ao3anFclSn153SsiCaVkO0wKAZiX vv22blQoZtXznB+FcaW6++2cKUAok9wx2tW6I/Ck= 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 6.18 171/480] ksmbd: fix use-after-free of a deferred file_lock on SMB2_CLOSE then SMB2_CANCEL Date: Thu, 16 Jul 2026 15:28:38 +0200 Message-ID: <20260716133048.408330267@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@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 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 @@ -7334,14 +7334,14 @@ 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,