From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D40A0138D for ; Tue, 3 Jan 2023 08:15:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59DA5C433D2; Tue, 3 Jan 2023 08:15:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672733706; bh=9G4Pv9Gt39/6SAjBBLxJSaHaXDOBFavoT07Za35EAVA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZADW0zGLSUnbtYiHhQvmCp0tgVq0Oi9Q1gAM9acG3RfFlsUWex1N/1+90x701KF4a ljQUPcAkt4JiOUv28MmEu3xkJQvt+Xx/Di+utf4/kWNxH2RVOMw/8tIkjlvQVYV8uY zXibq1x0LKMOZqJhCzSo7LD5yTZL0PNLqTRa1Emw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+c88a7030da47945a3cc3@syzkaller.appspotmail.com, Christian Brauner , Al Viro Subject: [PATCH 5.10 06/63] Make sure nd->path.mnt and nd->path.dentry are always valid pointers Date: Tue, 3 Jan 2023 09:13:36 +0100 Message-Id: <20230103081308.942805751@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230103081308.548338576@linuxfoundation.org> References: <20230103081308.548338576@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Al Viro [ Upstream commit 7d01ef7585c07afaf487759a48486228cd065726 ] Initialize them in set_nameidata() and make sure that terminate_walk() clears them once the pointers become potentially invalid (i.e. we leave RCU mode or drop them in non-RCU one). Currently we have "path_init() always initializes them and nobody accesses them outside of path_init()/terminate_walk() segments", which is asking for trouble. With that change we would have nd->path.{mnt,dentry} 1) always valid - NULL or pointing to currently allocated objects. 2) non-NULL while we are successfully walking 3) NULL when we are not walking at all 4) contributing to refcounts whenever non-NULL outside of RCU mode. Fixes: 6c6ec2b0a3e0 ("fs: add support for LOOKUP_CACHED") Reported-by: syzbot+c88a7030da47945a3cc3@syzkaller.appspotmail.com Tested-by: Christian Brauner Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/namei.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/namei.c +++ b/fs/namei.c @@ -529,6 +529,8 @@ static void set_nameidata(struct nameida p->stack = p->internal; p->dfd = dfd; p->name = name; + p->path.mnt = NULL; + p->path.dentry = NULL; p->total_link_count = old ? old->total_link_count : 0; p->saved = old; current->nameidata = p; @@ -602,6 +604,8 @@ static void terminate_walk(struct nameid rcu_read_unlock(); } nd->depth = 0; + nd->path.mnt = NULL; + nd->path.dentry = NULL; } /* path_put is needed afterwards regardless of success or failure */ @@ -2243,8 +2247,6 @@ static const char *path_init(struct name } nd->root.mnt = NULL; - nd->path.mnt = NULL; - nd->path.dentry = NULL; /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */ if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {