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Date: Fri, 5 Feb 2021 00:43:31 +0300
From: Alexander Popov <>
To: oss-security <>
 Linus Torvalds <>, Greg KH <>,
 "" <>,
 Norbert Slusarek <>,
 Stefano Garzarella <>, Eric Dumazet
 <>, Anthony Liguori <>,
 David Miller <>, Jakub Kicinski <>,
 Jorgen Hansen <>,
 Stefan Schmidt <>,
 Jeff Vander Stoep <>,
 Andrey Konovalov <>
Subject: Linux kernel: Exploitable vulnerabilities in AF_VSOCK implementation


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

I prepared the fixing patch and made responsible disclosure to Now the patch is merged into the mainline kernel:
  "vsock: fix the race conditions in multi-transport support"
This patch is also backported into the affected stable trees.

I've requested a CVE ID for these vulnerabilities at

Best regards,

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