linux-kernel - Re: [PATCH #2] reiserfs: Fix permissions on .reiserfs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <4BBE4227.7040206@gmail.com>
Date:	Thu, 08 Apr 2010 22:52:55 +0200
From:	Edward Shishkin <edward.shishkin@...il.com>
To:	Jeff Mahoney <jeffm@...e.com>
CC:	ReiserFS Mailing List <reiserfs-devel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH #2] reiserfs: Fix permissions on .reiserfs_priv

Jeff, it seems your MUA mangles patches,
would you please send it by another tool?

Thanks,
Edward.


Jeff Mahoney wrote:
>  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.
>
>  Re-sent because I forgot to turn off the GPG signing when I sent the first
>  time.
>
> Signed-off-by: Jeff Mahoney <jeffm@...e.com>
> ---
>
>  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
>   

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/