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Message-Id: <636E01BC-12FD-452B-8B1C-320B6EADAEFD@dubeyko.com>
Date: Sat, 21 Dec 2013 20:07:51 +0300
From: Vyacheslav Dubeyko <slava@...eyko.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-mtd@...ts.infradead.org, Mark Fasheh <mfasheh@...e.com>,
Joel Becker <jlbec@...lplan.org>,
reiserfs-devel@...r.kernel.org, xfs@....sgi.com,
jfs-discussion@...ts.sourceforge.net, cluster-devel@...hat.com,
linux-nfs@...r.kernel.org,
Andreas Gruenbacher <andreas.gruenbacher@...bit.com>
Subject: Re: [PATCH 21/21] hfsplus: remove can_set_xattr
On Dec 20, 2013, at 4:16 PM, Christoph Hellwig wrote:
> When using the per-superblock xattr handlers permission checking is
> done by the generic code. hfsplus just needs to check for the magic
> osx attribute not to leak into protected namespaces.
>
> Also given that the code was obviously copied from JFS the proper
> attribution was missing.
>
I don't think that this code changing is correct. Current modification
breaks logic. Please, see my comments below.
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> fs/hfsplus/xattr.c | 87 ++--------------------------------------------------
> 1 file changed, 3 insertions(+), 84 deletions(-)
>
> diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
> index bf88baa..0b4a5c9 100644
> --- a/fs/hfsplus/xattr.c
> +++ b/fs/hfsplus/xattr.c
> @@ -52,82 +52,6 @@ static inline int is_known_namespace(const char *name)
> return true;
> }
>
> -static int can_set_system_xattr(struct inode *inode, const char *name,
> - const void *value, size_t size)
I agree that it makes sense to remove this code if permission checking
is done by generic code.
> -{
> -#ifdef CONFIG_HFSPLUS_FS_POSIX_ACL
> - struct posix_acl *acl;
> - int err;
> -
> - if (!inode_owner_or_capable(inode))
> - return -EPERM;
> -
> - /*
> - * POSIX_ACL_XATTR_ACCESS is tied to i_mode
> - */
> - if (strcmp(name, POSIX_ACL_XATTR_ACCESS) == 0) {
> - acl = posix_acl_from_xattr(&init_user_ns, value, size);
> - if (IS_ERR(acl))
> - return PTR_ERR(acl);
> - if (acl) {
> - err = posix_acl_equiv_mode(acl, &inode->i_mode);
> - posix_acl_release(acl);
> - if (err < 0)
> - return err;
> - mark_inode_dirty(inode);
> - }
> - /*
> - * We're changing the ACL. Get rid of the cached one
> - */
> - forget_cached_acl(inode, ACL_TYPE_ACCESS);
> -
> - return 0;
> - } else if (strcmp(name, POSIX_ACL_XATTR_DEFAULT) == 0) {
> - acl = posix_acl_from_xattr(&init_user_ns, value, size);
> - if (IS_ERR(acl))
> - return PTR_ERR(acl);
> - posix_acl_release(acl);
> -
> - /*
> - * We're changing the default ACL. Get rid of the cached one
> - */
> - forget_cached_acl(inode, ACL_TYPE_DEFAULT);
> -
> - return 0;
> - }
> -#endif /* CONFIG_HFSPLUS_FS_POSIX_ACL */
> - return -EOPNOTSUPP;
> -}
> -
> -static int can_set_xattr(struct inode *inode, const char *name,
> - const void *value, size_t value_len)
This function works for all handlers. So, I don't think that it makes sense
to delete it.
> -{
> - if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
> - return can_set_system_xattr(inode, name, value, value_len);
> -
I agree that it needs to remove this check for XATTR_SYSTEM_PREFIX case.
> - if (!strncmp(name, XATTR_MAC_OSX_PREFIX, XATTR_MAC_OSX_PREFIX_LEN)) {
> - /*
> - * This makes sure that we aren't trying to set an
> - * attribute in a different namespace by prefixing it
> - * with "osx."
> - */
> - if (is_known_namespace(name + XATTR_MAC_OSX_PREFIX_LEN))
> - return -EOPNOTSUPP;
I think that this check is important. It forbids such combinations as "osx.system.*" or
"osx.trusted.*", for example. Because "osx.*" is virtual namespace for xattrs that
it can be under Mac OS X. If you want to set xattr from "system.*" namespace, for example,
then you need to use another handler. And such namespace should be without
addition of "osx." prefix.
> -
> - return 0;
> - }
> -
> - /*
> - * Don't allow setting an attribute in an unknown namespace.
> - */
> - if (strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) &&
> - strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) &&
> - strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
> - return -EOPNOTSUPP;
> -
> - return 0;
> -}
> -
> static void hfsplus_init_header_node(struct inode *attr_file,
> u32 clump_size,
> char *buf, u16 node_size)
> @@ -350,10 +274,6 @@ int __hfsplus_setxattr(struct inode *inode, const char *name,
> HFSPLUS_IS_RSRC(inode))
> return -EOPNOTSUPP;
>
> - err = can_set_xattr(inode, name, value, size);
The __hfsplus_setxattr() is common method for all handlers. So, removing
this call means that we don't check validity of namespace. I don't think
that such modification is a right way.
> - if (err)
> - return err;
> -
> if (strncmp(name, XATTR_MAC_OSX_PREFIX,
> XATTR_MAC_OSX_PREFIX_LEN) == 0)
> name += XATTR_MAC_OSX_PREFIX_LEN;
> @@ -841,10 +761,6 @@ int hfsplus_removexattr(struct dentry *dentry, const char *name)
> if (!HFSPLUS_SB(inode->i_sb)->attr_tree)
> return -EOPNOTSUPP;
>
> - err = can_set_xattr(inode, name, NULL, 0);
Ditto. Moreover, it is used namely hfsplus_removexattr() and not
__hfsplus_setxattr() for removing xattrs in hfsplus driver. So, removing
this check is not good way.
> - if (err)
> - return err;
> -
> if (strncmp(name, XATTR_MAC_OSX_PREFIX,
> XATTR_MAC_OSX_PREFIX_LEN) == 0)
> name += XATTR_MAC_OSX_PREFIX_LEN;
> @@ -941,6 +857,9 @@ static int hfsplus_osx_setxattr(struct dentry *dentry, const char *name,
> if (len > HFSPLUS_ATTR_MAX_STRLEN)
> return -EOPNOTSUPP;
>
> + if (is_known_namespace(name))
> + return -EOPNOTSUPP;
If common check in __hfsplus_setxattr() will be on the same place then
this addition doesn't make sense.
Thanks,
Vyacheslav Dubeyko.
> +
> strcpy(xattr_name, XATTR_MAC_OSX_PREFIX);
> strcpy(xattr_name + XATTR_MAC_OSX_PREFIX_LEN, name);
>
> --
> 1.7.10.4
>
>
> --
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