linux-kernel - Re: [PATCH 1/1] Drivers: hv: Fix bad ref to hv_synic_eventring

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] [day] [month] [year] [list]

Message-ID: <aAsq9RGFUbQUfQnl@liuwe-devbox-ubuntu-v2.tail21d00.ts.net>
Date: Fri, 25 Apr 2025 06:25:57 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc: mhklinux@...look.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com, kys@...rosoft.com,
	linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org
Subject: Re: [PATCH 1/1] Drivers: hv: Fix bad ref to hv_synic_eventring_tail
 when CPU goes offline

On Wed, Apr 23, 2025 at 10:50:27AM -0700, Nuno Das Neves wrote:
> On 4/21/2025 9:31 AM, mhkelley58@...il.com wrote:
> > From: Michael Kelley <mhklinux@...look.com>
> > 
> > When a CPU goes offline, hv_common_cpu_die() frees the
> > hv_synic_eventring_tail memory for the CPU. But in a normal VM (i.e., not
> > running in the root partition) the per-CPU memory has not been allocated,
> > resulting in a bad memory reference and oops when computing the argument
> > to kfree().
> > 
> > Fix this by freeing the memory only when running in the root partition.
> > 
> > Fixes: 04df7ac39943 ("Drivers: hv: Introduce per-cpu event ring tail")
> > Signed-off-by: Michael Kelley <mhklinux@...look.com>
> > ---
> >  drivers/hv/hv_common.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> > index b3b11be11650..8967010db86a 100644
> > --- a/drivers/hv/hv_common.c
> > +++ b/drivers/hv/hv_common.c
> > @@ -566,9 +566,11 @@ int hv_common_cpu_die(unsigned int cpu)
> >  	 * originally allocated memory is reused in hv_common_cpu_init().
> >  	 */
> >  
> > -	synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail);
> > -	kfree(*synic_eventring_tail);
> > -	*synic_eventring_tail = NULL;
> > +	if (hv_root_partition()) {
> > +		synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail);
> > +		kfree(*synic_eventring_tail);
> > +		*synic_eventring_tail = NULL;
> > +	}
> >  
> >  	return 0;
> >  }
> 
> Reviewed-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>

Applied to hyperv-fixes.