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authorJeff Mahoney <jeffm@suse.com>2010-04-23 13:17:37 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-04-24 11:31:24 -0700
commitcac36f707119b792b2396aed371d6b5cdc194890 (patch)
treeccb19a68ce1c1aa066d6d13dde51657cba906de6 /fs/reiserfs/xattr.c
parent33eaf788345c0311ab48ae62673c05f59fb09bb3 (diff)
reiserfs: fix permissions on .reiserfs_priv
Commit 677c9b2e393a0cd203bd54e9c18b012b2c73305a ("reiserfs: remove privroot hiding in lookup") 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 unprivileged 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 <jeffm@suse.com> Acked-by: Edward Shishkin <edward.shishkin@gmail.com> Reported-by: Matt McCutchen <matt@mattmccutchen.net> Tested-by: Matt McCutchen <matt@mattmccutchen.net> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/reiserfs/xattr.c')
-rw-r--r--fs/reiserfs/xattr.c17
1 files changed, 4 insertions, 13 deletions
diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index 4f9586bb763..28f0a448f3c 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -973,21 +973,13 @@ int reiserfs_permission(struct inode *inode, int mask)
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)
@@ -1001,8 +993,7 @@ int reiserfs_lookup_privroot(struct super_block *s)
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