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Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

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Pull overlayfs fix from Miklos Szeredi:
 "This fixes a regression introduced in this cycle"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix possible use after free on redirect dir lookup
This commit is contained in:
Linus Torvalds 2017-01-20 11:58:30 -08:00
commit 56ef18829e
1 changed files with 18 additions and 9 deletions
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27
fs/overlayfs/namei.c
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@ -154,29 +154,38 @@ out_err:
static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
struct dentry **ret)
{
const char *s = d->name.name;
/* Counting down from the end, since the prefix can change */
size_t rem = d->name.len - 1;
struct dentry *dentry = NULL;
int err;
if (*s != '/')
if (d->name.name[0] != '/')
return ovl_lookup_single(base, d, d->name.name, d->name.len,
0, "", ret);
while (*s++ == '/' && !IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
const char *s = d->name.name + d->name.len - rem;
const char *next = strchrnul(s, '/');
size_t slen = strlen(s);
size_t thislen = next - s;
bool end = !next[0];
if (WARN_ON(slen > d->name.len) ||
WARN_ON(strcmp(d->name.name + d->name.len - slen, s)))
/* Verify we did not go off the rails */
if (WARN_ON(s[-1] != '/'))
return -EIO;
err = ovl_lookup_single(base, d, s, next - s,
d->name.len - slen, next, &base);
err = ovl_lookup_single(base, d, s, thislen,
d->name.len - rem, next, &base);
dput(dentry);
if (err)
return err;
dentry = base;
s = next;
if (end)
break;
rem -= thislen + 1;
if (WARN_ON(rem >= d->name.len))
return -EIO;
}
*ret = dentry;
return 0;