Date: Fri, 05 Feb 2021 18:33:26 +0300 From: Alexander Popov <alex.popov@...ux.com> To: oss-security <oss-security@...ts.openwall.com> CC: linux-distros@...openwall.org,Linus Torvalds <torvalds@...uxfoundation.org>,Greg KH <greg@...ah.com>,"security@...nel.org" <security@...nel.org>,Norbert Slusarek <nslusarek@....net>,Stefano Garzarella <sgarzare@...hat.com>,Eric Dumazet <edumazet@...gle.com>,Anthony Liguori <aliguori@...zon.com>,David Miller <davem@...emloft.net>,Jakub Kicinski <kuba@...nel.org>,Jorgen Hansen <jhansen@...are.com>,Stefan Schmidt <stefan@...enfreihafen.org>,Jeff Vander Stoep <jeffv@...gle.com>,Andrey Konovalov <andreyknvl@...gle.com> Subject: Re: Linux kernel: Exploitable vulnerabilities in AF_VSOCK implementation On February 5, 2021 12:43:31 AM GMT+03:00, Alexander Popov <alex.popov@...ux.com> wrote: >Hello! > >Let me inform you about the Linux kernel vulnerabilities that I've >found in >AF_VSOCK implementation. I managed to exploit one of them for a local >privilege >escalation on Fedora Server 33 for x86_64, bypassing SMEP and SMAP. I'm >going to >share all the details about the exploit techniques later. > >CONFIG_VSOCKETS and CONFIG_VIRTIO_VSOCKETS are shipped as kernel >modules in all >major GNU/Linux distributions. The vulnerable modules are automatically >loaded >when you create a socket for AF_VSOCK. That is available for >unprivileged users >and user namespaces are not needed for that. > >These vulnerabilities are race conditions caused by wrong locking in >net/vmw_vsock/af_vsock.c. The race conditions were implicitly >introduced in >November 2019 in the commits c0cfa2d8a788fcf4 and 6a2c0962105ae8ce that >added >VSOCK multi-transport support. These commits were merged in the Linux >kernel >v5.5-rc1. > >I prepared the fixing patch and made responsible disclosure to >security@...nel.org. Now the patch is merged into the mainline kernel: > "vsock: fix the race conditions in multi-transport support" > >https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c518adafa39f37858697ac9309c6cf1805581446 >This patch is also backported into the affected stable trees. > >I've requested a CVE ID for these vulnerabilities at >https://cveform.mitre.org/. CVE-2021-26708 is assigned to these issues: https://nvd.nist.gov/vuln/detail/CVE-2021-26708 Best regards, Alexander
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