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From: David Howells <>
To: Chris von Recklinghausen <>
	Jarkko Sakkinen <>,
	James Morris <>,
	"Serge E . Hallyn" <>,,,, Waiman Long <>
Subject: Re: [PATCH] security/keyring: avoid pagefaults in keyring_read_iterator
Date: Mon, 21 Oct 2019 15:21:59 +0100
Message-ID: <> (raw)
In-Reply-To: <>

Chris von Recklinghausen <> 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


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Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18 18:40 Chris von Recklinghausen
2019-10-21 14:21 ` David Howells [this message]
2019-10-21 15:46   ` Chris von Recklinghausen
2019-10-25 11:10     ` Chris von Recklinghausen
2019-11-06 15:25       ` Chris von Recklinghausen
2019-10-21 15:47 ` Jarkko Sakkinen

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