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 0437D20F88 for ; Fri, 21 Jul 2023 19:10:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A3B2C433C7; Fri, 21 Jul 2023 19:10:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689966637; bh=YWNF1zzNFQ7y1wDpyc44tr/EblJIlqfHJqYDmnCsMs8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LNucWpk3yv/Qhsi1ohHmuQrfwD+0vIGfOjw7Dm/92BXE1z8neOk2BI5ewFNfQYj7w LwPq+w+tg7VL7vPjiJpoIex+wyik9ziVe2fHa20Sw/gonezRKSfkNFfHNJM/eI0JM7 uikydAV1tdjtc2azQq7AOpFQWo2QnTZbbBdrZkSg= 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 5.15 377/532] ovl: fix null pointer dereference in ovl_get_acl_rcu() Date: Fri, 21 Jul 2023 18:04:41 +0200 Message-ID: <20230721160634.942148619@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230721160614.695323302@linuxfoundation.org> References: <20230721160614.695323302@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 | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -453,7 +453,15 @@ struct posix_acl *ovl_get_acl(struct ino const struct cred *old_cred; struct posix_acl *acl; - if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode)) + if (!IS_ENABLED(CONFIG_FS_POSIX_ACL)) + return NULL; + + if (!realinode) { + WARN_ON(!rcu); + return ERR_PTR(-ECHILD); + } + + if (!IS_POSIXACL(realinode)) return NULL; if (rcu)