Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] security/keyring: avoid pagefaults in keyring_read_iterator | Date | Mon, 21 Oct 2019 15:21:59 +0100 |
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Chris von Recklinghausen <crecklin@redhat.com> wrote:
> The put_user call from keyring_read_iterator caused a page fault which > attempts to lock mm->mmap_sem and type->lock_class (key->sem) in the reverse > order that keyring_read_iterator did, thus causing the circular locking > dependency. > > Remedy this by using access_ok and __put_user instead of put_user so we'll > return an error instead of faulting in the page.
I wonder if it's better to create a kernel buffer outside of the lock in keyctl_read_key(). Hmmm... The reason I didn't want to do that is that keyrings have don't have limits on the size. Maybe that's not actually a problem, since 1MiB would be able to hold a list of a quarter of a million keys.
David
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