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 B4C318F5B for ; Sun, 16 Jul 2023 20:29:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 39F0FC433C7; Sun, 16 Jul 2023 20:29:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689539377; bh=fGOPGcvrboWGfiqg4qr/av+TDNZV0E2tA3tsdejsHXI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gNbQgOPs9qQuwYKpshgwtw0kih+wmw2mUmZBsoPmMXu4KUJxVCjsjiCSScegrfduG miqy39zPoqxbwuhhwtPnLBRuuZ6ABpIpTEFsA8ChSucKqzC+NbZdmlraCeQCwwAv6/ mxxgGHe8ffoZ5fwTYOXu+DySq0H4GoDQtQCPExDw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zhihao Cheng , Christian Brauner , Amir Goldstein , Miklos Szeredi Subject: [PATCH 6.4 785/800] ovl: fix null pointer dereference in ovl_get_acl_rcu() Date: Sun, 16 Jul 2023 21:50:38 +0200 Message-ID: <20230716195007.380636900@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194949.099592437@linuxfoundation.org> References: <20230716194949.099592437@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: Zhihao Cheng commit f4e19e595cc2e76a8a58413eb19d3d9c51328b53 upstream. Following process: P1 P2 path_openat link_path_walk may_lookup inode_permission(rcu) ovl_permission acl_permission_check check_acl get_cached_acl_rcu ovl_get_inode_acl realinode = ovl_inode_real(ovl_inode) drop_cache __dentry_kill(ovl_dentry) iput(ovl_inode) ovl_destroy_inode(ovl_inode) dput(oi->__upperdentry) dentry_kill(upperdentry) dentry_unlink_inode upperdentry->d_inode = NULL ovl_inode_upper upperdentry = ovl_i_dentry_upper(ovl_inode) d_inode(upperdentry) // returns NULL IS_POSIXACL(realinode) // NULL pointer dereference , will trigger an null pointer dereference at realinode: [ 205.472797] BUG: kernel NULL pointer dereference, address: 0000000000000028 [ 205.476701] CPU: 2 PID: 2713 Comm: ls Not tainted 6.3.0-12064-g2edfa098e750-dirty #1216 [ 205.478754] RIP: 0010:do_ovl_get_acl+0x5d/0x300 [ 205.489584] Call Trace: [ 205.489812] [ 205.490014] ovl_get_inode_acl+0x26/0x30 [ 205.490466] get_cached_acl_rcu+0x61/0xa0 [ 205.490908] generic_permission+0x1bf/0x4e0 [ 205.491447] ovl_permission+0x79/0x1b0 [ 205.491917] inode_permission+0x15e/0x2c0 [ 205.492425] link_path_walk+0x115/0x550 [ 205.493311] path_lookupat.isra.0+0xb2/0x200 [ 205.493803] filename_lookup+0xda/0x240 [ 205.495747] vfs_fstatat+0x7b/0xb0 Fetch a reproducer in [Link]. Use the helper ovl_i_path_realinode() to get realinode and then do non-nullptr checking. Link: https://bugzilla.kernel.org/show_bug.cgi?id=217404 Fixes: 332f606b32b6 ("ovl: enable RCU'd ->get_acl()") Cc: # v5.15 Signed-off-by: Zhihao Cheng Suggested-by: Christian Brauner Suggested-by: Amir Goldstein Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/inode.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -558,20 +558,20 @@ struct posix_acl *do_ovl_get_acl(struct struct inode *inode, int type, bool rcu, bool noperm) { - struct inode *realinode = ovl_inode_real(inode); + struct inode *realinode; struct posix_acl *acl; struct path realpath; - if (!IS_POSIXACL(realinode)) - return NULL; - /* Careful in RCU walk mode */ - ovl_i_path_real(inode, &realpath); - if (!realpath.dentry) { + realinode = ovl_i_path_real(inode, &realpath); + if (!realinode) { WARN_ON(!rcu); return ERR_PTR(-ECHILD); } + if (!IS_POSIXACL(realinode)) + return NULL; + if (rcu) { /* * If the layer is idmapped drop out of RCU path walk