From: Michael Ellerman <mpe@ellerman.id.au>
To: oss-security@lists.openwall.com
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Linux kernel: powerpc: KVM guest to host memory corruption
Date: Mon, 26 Jul 2021 19:13:25 +1000 [thread overview]
Message-ID: <87im0x1lqi.fsf@mpe.ellerman.id.au> (raw)
The Linux kernel for powerpc since v3.10 has a bug which allows a malicious KVM guest to
corrupt host memory.
In the handling of the H_RTAS hypercall, args.rets is made to point into the args.args
buffer which is located on the stack:
args.rets = &args.args[be32_to_cpu(args.nargs)];
However args.nargs has not been range checked. That allows the guest to point args.rets
anywhere up to +16GB from args.args.
The guest does not have control of what is written to args.rets, it is always (u32)-3,
because subsequent code does check nargs. Additionally the guest will be killed as a
result of the nargs being out of range, so a given guest only has a single shot at
corrupting memory.
Only machines using Linux as the hypervisor, aka. KVM or bare metal, are affected by the
bug.
The bug was introduced in:
8e591cb72047 ("KVM: PPC: Book3S: Add infrastructure to implement kernel-side RTAS calls")
Which was first released in v3.10.
The upstream fix is:
f62f3c20647e ("KVM: PPC: Book3S: Fix H_RTAS rets buffer overflow")
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f62f3c20647ebd5fb6ecb8f0b477b9281c44c10a
Which will be included in the v5.14 release.
cheers
next reply other threads:[~2021-07-26 9:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 9:13 Michael Ellerman [this message]
2021-07-27 0:46 ` Linux kernel: powerpc: KVM guest to host memory corruption Michael Ellerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87im0x1lqi.fsf@mpe.ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=oss-security@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).