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ovl: check mounter creds on underlying lookup

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The hash salting changes meant that we can no longer reuse the hash in the
overlay dentry to look up the underlying dentry.

Instead of lookup_hash(), use lookup_one_len_unlocked() and swith to
mounter's creds (like we do for all other operations later in the series).

Now the lookup_hash() export introduced in 4.6 by 3c9fe8cdff ("vfs: add
lookup_hash() helper") is unused and can possibly be removed; its
usefulness negated by the hash salting and the idea that mounter's creds
should be used on operations on underlying filesystems.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 8387ff2577 ("vfs: make the string hashes salt the hash")
This commit is contained in:
Miklos Szeredi 2016-07-29 12:05:22 +02:00
parent 1b91dbdd29
commit c1b2cc1a76
1 changed files with 9 additions and 4 deletions
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13
fs/overlayfs/super.c
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@ -423,12 +423,16 @@ static bool ovl_dentry_weird(struct dentry *dentry)
DCACHE_OP_COMPARE);
}
static inline struct dentry *ovl_lookup_real(struct dentry *dir,
static inline struct dentry *ovl_lookup_real(struct super_block *ovl_sb,
struct dentry *dir,
struct qstr *name)
{
const struct cred *old_cred;
struct dentry *dentry;
dentry = lookup_hash(name, dir);
old_cred = ovl_override_creds(ovl_sb);
dentry = lookup_one_len_unlocked(name->name, dir, name->len);
revert_creds(old_cred);
if (IS_ERR(dentry)) {
if (PTR_ERR(dentry) == -ENOENT)
@ -481,7 +485,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
upperdir = ovl_upperdentry_dereference(poe);
if (upperdir) {
this = ovl_lookup_real(upperdir, &dentry->d_name);
this = ovl_lookup_real(dentry->d_sb, upperdir, &dentry->d_name);
err = PTR_ERR(this);
if (IS_ERR(this))
goto out;
@ -514,7 +518,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
bool opaque = false;
struct path lowerpath = poe->lowerstack[i];
this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
this = ovl_lookup_real(dentry->d_sb,
lowerpath.dentry, &dentry->d_name);
err = PTR_ERR(this);
if (IS_ERR(this)) {
/*