linux-kernel - oopsable race in xen-gntdev (unsafe vma access)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121215181211.GV4939@ZenIV.linux.org.uk>
Date:	Sat, 15 Dec 2012 18:12:11 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	linux-kernel@...r.kernel.org
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: oopsable race in xen-gntdev (unsafe vma access)

	1) find_vma() is *not* safe without ->mmap_sem and its result may
very well be freed just as it's returned to caller.  IOW,
gntdev_ioctl_get_offset_for_vaddr() is racy and may end up with
dereferencing freed memory.

	2) gntdev_vma_close() is putting NULL into map->vma with only
->mmap_sem held by caller.  Things like
                if (!map->vma)
                        continue;
                if (map->vma->vm_start >= end)
                        continue;
                if (map->vma->vm_end <= start)
done with just priv->lock held are racy.

	I'm not familiar with the code, but it looks like we need to
protect gntdev_vma_close() guts with the same spinlock and probably
hold ->mmap_sem shared around the "find_vma()+get to map->{index,count}"
in the ioctl.  Or replace the logics in ioctl with search through the
list of grant_map under the same spinlock...

	Comments?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/