From: Jeff Mahoney Subject: [PATCH] reiserfs: Fix permissions on .reiserfs_priv References: bnc#593906 CVE-2010-1146 Patch-mainline: Submitted 8 Apr 2010 Commit 677c9b2e393a0cd203bd54e9c18b012b2c73305a removed the magic from the lookup code to hide the .reiserfs_priv directory since it was getting loaded at mount-time instead. The intent was that the entry would be hidden from the user via a poisoned d_compare, but this was faulty. This introduced a security issue where unpriviledged users could access and modify extended attributes or ACLs belonging to other users, including root. This patch resolves the issue by properly hiding .reiserfs_priv. This was the intent of the xattr poisoning code, but it appears to have never worked as expected. This is fixed by using d_revalidate instead of d_compare. This patch makes -oexpose_privroot a no-op. I'm fine leaving it this way. The effort involved in working out the corner cases wrt permissions and caching outweigh the benefit of the feature. Signed-off-by: Jeff Mahoney --- fs/reiserfs/dir.c | 2 -- fs/reiserfs/xattr.c | 17 ++++------------- 2 files changed, 4 insertions(+), 15 deletions(-) --- a/fs/reiserfs/dir.c +++ b/fs/reiserfs/dir.c @@ -45,8 +45,6 @@ static inline bool is_privroot_deh(struc struct reiserfs_de_head *deh) { struct dentry *privroot = REISERFS_SB(dir->d_sb)->priv_root; - if (reiserfs_expose_privroot(dir->d_sb)) - return 0; return (dir == dir->d_parent && privroot->d_inode && deh->deh_objectid == INODE_PKEY(privroot->d_inode)->k_objectid); } --- a/fs/reiserfs/xattr.c +++ b/fs/reiserfs/xattr.c @@ -972,21 +972,13 @@ int reiserfs_permission(struct inode *in return generic_permission(inode, mask, NULL); } -/* This will catch lookups from the fs root to .reiserfs_priv */ -static int -xattr_lookup_poison(struct dentry *dentry, struct qstr *q1, struct qstr *name) +static int xattr_hide_revalidate(struct dentry *dentry, struct nameidata *nd) { - struct dentry *priv_root = REISERFS_SB(dentry->d_sb)->priv_root; - if (container_of(q1, struct dentry, d_name) == priv_root) - return -ENOENT; - if (q1->len == name->len && - !memcmp(q1->name, name->name, name->len)) - return 0; - return 1; + return -EPERM; } static const struct dentry_operations xattr_lookup_poison_ops = { - .d_compare = xattr_lookup_poison, + .d_revalidate = xattr_hide_revalidate, }; int reiserfs_lookup_privroot(struct super_block *s) @@ -1000,8 +992,7 @@ int reiserfs_lookup_privroot(struct supe strlen(PRIVROOT_NAME)); if (!IS_ERR(dentry)) { REISERFS_SB(s)->priv_root = dentry; - if (!reiserfs_expose_privroot(s)) - s->s_root->d_op = &xattr_lookup_poison_ops; + dentry->d_op = &xattr_lookup_poison_ops; if (dentry->d_inode) dentry->d_inode->i_flags |= S_PRIVATE; } else