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 E1A60347BC1; Thu, 2 Jul 2026 16:22:54 +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=1783009377; cv=none; b=ij0kbvJXmBzXLDx8QLkeJ5+LAPuoqkvQmU6lvRJ1g7h/M4IfGaciV0HrFsdePGGQ0VKlRebB4UZKHCe8yrfRwzsqQfLfckPCH6IQocfJ17c96kkCiRC4LLecEe6TgzKzhVbXgJg55qVSZAtmDwAuB2xut/KDQlwh4bSnEBG12ds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783009377; c=relaxed/simple; bh=gqgjW2FLqeukFfcoKR6wjxokd2lCk6ekRsNATvpfNcQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NmxLDHihEvQHk/adU8VrqcAJl+248zujGJhIvbvIbQFUkSyyDShNHiuEFDx0B0R5ZvumqgisO4vpGAi+4V8RioFuS35Z3iSWiV02u/Y3QqC+KvkxS7ao0dIbexVxPcR9i28qqg0c94sZiw23oAxsJBV2pw4fXLqpa3h1knmWGUw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZnLY2TXB; 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="ZnLY2TXB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F89A1F000E9; Thu, 2 Jul 2026 16:22:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783009374; bh=nQxX/whZsVOa4ku1EVVhr7xuswtHIZUnbSiCpeKO22c=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZnLY2TXBwQ7wszkYkeVwyPneWy0B0DvwRX1aIlA7BMZrGuIzbNcMe5NDBWILt2OGj xQOUfmyeu3M0erKGS684MsTWPEFdiGS6688Jp8VbWmkl7kN64f15A3cbq94mLhLsTK qPLTyQL9KyRJjCB/G6D20GdpyUmkFyK/HKWN5i3g= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yi Yang , Jiri Slaby Subject: [PATCH 5.10 27/96] vc_screen: fix null-ptr-deref in vcs_notifier() during concurrent vcs_write Date: Thu, 2 Jul 2026 18:19:19 +0200 Message-ID: <20260702155109.556508135@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155108.949633242@linuxfoundation.org> References: <20260702155108.949633242@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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yi Yang commit a287620312dc6dcb9a093417a0e589bf30fcf38a upstream. A KASAN null-ptr-deref was observed in vcs_notifier(): BUG: KASAN: null-ptr-deref in vcs_notifier+0x98/0x130 Read of size 2 at addr qmp_cmd_name: qmp_capabilities, arguments: {} The issue is a race condition in vcs_write(). When the console_lock is temporarily dropped (to copy data from userspace), the vc_data pointer obtained from vcs_vc() may become stale. After re-acquiring the lock, vcs_vc() is called again to re-validate the pointer. If the vc has been deallocated in the meantime, vcs_vc() returns NULL, and the while loop breaks (with written > 0). However, after the loop, vcs_scr_updated(vc) is still called with the now-NULL vc pointer, leading to a null pointer dereference in the notifier chain (vcs_notifier dereferences param->vc). Fix this by adding a NULL check for vc before calling vcs_scr_updated(). Fixes: 8fb9ea65c9d1 ("vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF") Cc: stable@vger.kernel.org Signed-off-by: Yi Yang Reviewed-by: Jiri Slaby Link: https://patch.msgid.link/20260604060734.2914976-1-yiyang13@huawei.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vc_screen.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/tty/vt/vc_screen.c +++ b/drivers/tty/vt/vc_screen.c @@ -699,7 +699,7 @@ vcs_write(struct file *file, const char } *ppos += written; ret = written; - if (written) + if (written && vc) vcs_scr_updated(vc); unlock_out: