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Date: Sun, 24 Jan 2016 13:03:13 -0500 (EST)
From: cve-assign@...re.org
To: carnil@...ian.org
Cc: cve-assign@...re.org, oss-security@...ts.openwall.com
Subject: Re: CVE Request: Linux: fuse: possible denial of service in fuse_fill_write_pages()

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> https://bugzilla.redhat.com/show_bug.cgi?id=1290642
> https://git.kernel.org/linus/3ca8138f014a913f98e6ef40e939868e1e9ea876

> I got a report about unkillable task eating CPU. Further investigation
> shows, that the problem is in the fuse_fill_write_pages() function. If
> iov's first segment has zero length, we get an infinite loop, because
> we never reach iov_iter_advance() call.

Use CVE-2015-8785.


> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=124d3b7041f9a0ca7c43a6293e1cae4576c32fd5

> Frederik Himpe reported an unkillable and un-straceable pan process.

> Zero length iovecs can go into an infinite loop in writev, because the
> iovec iterator does not always advance over them.

> The sequence required to trigger this is not trivial. I think it
> requires that a zero-length iovec be followed by a non-zero-length
> iovec which causes a pagefault in the atomic usercopy. This causes the
> writev code to drop back into single-segment copy mode, which then
> tries to copy the 0 bytes of the zero-length iovec; a zero length copy
> looks like a failure though, so it loops.

Use CVE-2008-7316.

- -- 
CVE assignment team, MITRE CVE Numbering Authority
M/S M300
202 Burlington Road, Bedford, MA 01730 USA
[ PGP key available through http://cve.mitre.org/cve/request_id.html ]
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