linux-kernel - Re: [PATCH v1 1/2] KVM: s390: Fix incorrect usage of mmu_notifier

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

Message-ID: <20250805121620.40333-A-seiden@linux.ibm.com>
Date: Tue, 5 Aug 2025 14:16:20 +0200
From: Steffen Eiden <seiden@...ux.ibm.com>
To: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, david@...hat.com, frankja@...ux.ibm.com,
        nsg@...ux.ibm.com, nrb@...ux.ibm.com, schlameuss@...ux.ibm.com,
        hca@...ux.ibm.com, mhartmay@...ux.ibm.com, borntraeger@...ibm.com
Subject: Re: [PATCH v1 1/2] KVM: s390: Fix incorrect usage of
 mmu_notifier_register()

On Tue, Aug 05, 2025 at 01:14:45PM +0200, Claudio Imbrenda wrote:
> If mmu_notifier_register() fails, for example because a signal was
> pending, the mmu_notifier will not be registered. But when the VM gets
> destroyed, it will get unregistered anyway and that will cause one
> extra mmdrop(), which will eventually cause the mm of the process to
> be freed too early, and cause a use-after free.
> 
> This bug happens rarely, and only when secure guests are involved.
> 
> The solution is to check the return value of mmu_notifier_register()
> and return it to the caller (ultimately it will be propagated all the
> way to userspace). In case of -EINTR, userspace will try again.
> 
> Fixes: ca2fd0609b5d ("KVM: s390: pv: add mmu_notifier")
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

Reviewed-by: Steffen Eiden <seiden@...ux.ibm.com>