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userns: unshare_userns(&cred) should not populate cred on failure

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unshare_userns(new_cred) does *new_cred = prepare_creds() before
create_user_ns() which can fail. However, the caller expects that
it doesn't need to take care of new_cred if unshare_userns() fails.

We could change the single caller, sys_unshare(), but I think it
would be more clean to avoid the side effects on failure, so with
this patch unshare_userns() does put_cred() itself and initializes
*new_cred only if create_user_ns() succeeeds.

Cc: stable@vger.kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2013-08-06 19:38:55 +02:00 committed by Linus Torvalds
parent c095ba7224
commit 6160968cee
1 changed files with 9 additions and 4 deletions
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13
kernel/user_namespace.c
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@ -105,16 +105,21 @@ int create_user_ns(struct cred *new)
int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
{
struct cred *cred;
int err = -ENOMEM;
if (!(unshare_flags & CLONE_NEWUSER))
return 0;
cred = prepare_creds();
if (!cred)
return -ENOMEM;
if (cred) {
err = create_user_ns(cred);
if (err)
put_cred(cred);
else
*new_cred = cred;
}
*new_cred = cred;
return create_user_ns(cred);
return err;
}
void free_user_ns(struct user_namespace *ns)