| Message ID | 20180513160341.GN30522@ZenIV.linux.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, May 13, 2018 at 05:03:42PM +0100, Al Viro wrote: > Making something exportable takes more than providing ->s_export_ops. > In particular, ->lookup() *MUST* use d_splice_alias() instead of > d_add(). > > Reading Documentation/filesystems/nfs/Exporting would've been a good idea; > as it is, exporting AFFS is badly (and exploitably) broken. > > Partially-Fixes: ed4433d72394 "fs/affs: make affs exportable" > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: David Sterba <dsterba@suse.com>
> On 13 May 2018 at 18:03 Al Viro <viro@ZenIV.linux.org.uk> wrote: > > > Making something exportable takes more than providing ->s_export_ops. > In particular, ->lookup() *MUST* use d_splice_alias() instead of > d_add(). > > Reading Documentation/filesystems/nfs/Exporting would've been a good idea; > as it is, exporting AFFS is badly (and exploitably) broken. Hi Al, Could you tell me where Affs is broken ? affs_get_parent() uses d_obtain_alias() and your patch fixes the lookup. Do you suggest other updates or to mark nfs support experimental in AFFS or something else ? (btw, other export functions are fh_to_dentry using generic_fh_to_dentry() fh_to_parent using generic_fh_to_parent() ) Regards, Fabian
diff --git a/fs/affs/namei.c b/fs/affs/namei.c index 1ed0fa4c4d48..41c5749f4db7 100644 --- a/fs/affs/namei.c +++ b/fs/affs/namei.c @@ -201,6 +201,7 @@ affs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) struct super_block *sb = dir->i_sb; struct buffer_head *bh; struct inode *inode = NULL; + struct dentry *res; pr_debug("%s(\"%pd\")\n", __func__, dentry); @@ -223,14 +224,12 @@ affs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) } affs_brelse(bh); inode = affs_iget(sb, ino); - if (IS_ERR(inode)) { - affs_unlock_dir(dir); - return ERR_CAST(inode); - } } - d_add(dentry, inode); + res = d_splice_alias(inode, dentry); + if (!IS_ERR_OR_NULL(res)) + res->d_fsdata = dentry->d_fsdata; affs_unlock_dir(dir); - return NULL; + return res; } int
Making something exportable takes more than providing ->s_export_ops. In particular, ->lookup() *MUST* use d_splice_alias() instead of d_add(). Reading Documentation/filesystems/nfs/Exporting would've been a good idea; as it is, exporting AFFS is badly (and exploitably) broken. Partially-Fixes: ed4433d72394 "fs/affs: make affs exportable" Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>