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reiserfs: fix permissions on .reiserfs_priv 

Commit 677c9b2e39 ("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>
This commit is contained in:
Jeff Mahoney 2010-04-23 13:17:37 -04:00 committed by Linus Torvalds
parent 33eaf78834
commit cac36f7071
2 changed files with 4 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/reiserfs/dir.c
View File

@ -46,8 +46,6 @@ static inline bool is_privroot_deh(struct dentry *dir,
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);
}

17
fs/reiserfs/xattr.c
View File

@ -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