| 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
| ||
|
Message-ID: <zkamzruq5e3diahm7vyjansnaowkw42toh5evwgq6vqal7h4pk@3w4e47ggogyr>
Date: Thu, 7 Nov 2024 11:03:28 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: jasowang@...hat.com, mst@...hat.com, michael.christie@...cle.com,
linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org
Subject: Re: [PATCH v3 7/9] vhost: Add new UAPI to support change to task mode
On Thu, Nov 07, 2024 at 03:12:49PM +0800, Cindy Lu wrote:
>On Tue, Nov 5, 2024 at 6:32 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>>
>> On Tue, Nov 05, 2024 at 03:25:26PM +0800, Cindy Lu wrote:
>> >Add a new UAPI to enable setting the vhost device to task mode.
>> >The userspace application can use VHOST_SET_INHERIT_FROM_OWNER
>> >to configure the mode if necessary.
>> >This setting must be applied before VHOST_SET_OWNER, as the worker
>> >will be created in the VHOST_SET_OWNER function
>> >
>> >Signed-off-by: Cindy Lu <lulu@...hat.com>
>> >---
>> > drivers/vhost/vhost.c | 15 ++++++++++++++-
>> > include/uapi/linux/vhost.h | 2 ++
>> > 2 files changed, 16 insertions(+), 1 deletion(-)
>> >
>> >diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> >index c17dc01febcc..70c793b63905 100644
>> >--- a/drivers/vhost/vhost.c
>> >+++ b/drivers/vhost/vhost.c
>> >@@ -2274,8 +2274,9 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
>> > {
>> > struct eventfd_ctx *ctx;
>> > u64 p;
>> >- long r;
>> >+ long r = 0;
>>
>> I don't know if something is missing in this patch, but I am confused:
>>
>> `r` is set few lines below...
>>
>> > int i, fd;
>> >+ bool inherit_owner;
>> >
>> > /* If you are not the owner, you can become one */
>> > if (ioctl == VHOST_SET_OWNER) {
>> ...
>>
>> /* You must be the owner to do anything else */
>> r = vhost_dev_check_owner(d);
>> if (r)
>> goto done;
>>
>> So, why we are now initializing it to 0?
>>
>r = 0 mean return successfully here.
>Therefore, in the case VHOST_SET_INHERIT_FROM_OWNER function, I don't
>need to set it again and can simply return.
>....
> if (vhost_dev_has_owner(d))
> break;
>.....
Okay, but vhost_dev_check_owner() already set it to 0, so we can avoid
that, no?
>> >@@ -2332,6 +2333,18 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
>> > if (ctx)
>> > eventfd_ctx_put(ctx);
>> > break;
>> >+ case VHOST_SET_INHERIT_FROM_OWNER:
>> >+ /*inherit_owner can only be modified before owner is set*/
>> >+ if (vhost_dev_has_owner(d))
>>
>> And here, how this check can be false, if at the beginning of the
>> function we call vhost_dev_check_owner()?
>>
>> Maybe your intention was to add this code before the
>> `vhost_dev_check_owner()` call, so this should explain why initialize
>> `r` to 0, but I'm not sure.
>>
>Yes, in the function beginning, the code is
>if (ioctl == VHOST_SET_OWNER) {
>r = vhost_dev_set_owner(d);
>goto done;
>}
>if the ioctl is not VHOST_SET_OWNER, then the code will not run the
>function vhost_dev_set_owner.
Sorry, I meant vhost_dev_check_owner(), not vhost_dev_set_owner().
I'll try to explain again.
After applying this series we have this code:
long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
{
struct eventfd_ctx *ctx;
u64 p;
long r = 0;
int i, fd;
bool inherit_owner;
/* If you are not the owner, you can become one */
if (ioctl == VHOST_SET_OWNER) {
r = vhost_dev_set_owner(d);
goto done;
}
/* You must be the owner to do anything else */
r = vhost_dev_check_owner(d);
if (r)
goto done;
switch (ioctl) {
...
case VHOST_SET_INHERIT_FROM_OWNER:
/*inherit_owner can only be modified before owner is
* set*/
if (vhost_dev_has_owner(d))
break;
IIUC this check is always true, so we always call `break` because at
the beginning of this function we call vhost_dev_check_owner() which
if `dev->mm != current->mm` (so it can't be null I guess) jumps directly
into `done`, returning an error.
So I still don't understand in which condition we can run the code after
this check.
Thanks,
Stefano
if (copy_from_user(&inherit_owner, argp,
sizeof(inherit_owner))) {
r = -EFAULT;
break;
}
d->inherit_owner = inherit_owner;
break;
>This ioctl is used by userspace applications, so we cannot be certain
>of the type and sequence of their calls; therefore, I added this
>check.
>
>> >+ break;
>>
>> Should we return an error (e.g. -EPERM) in this case?
>>
>sure，will add this back
>thanks
>Cindy
>> >+
>> >+ if (copy_from_user(&inherit_owner, argp,
>> >+ sizeof(inherit_owner))) {
>> >+ r = -EFAULT;
>> >+ break;
>> >+ }
>> >+ d->inherit_owner = inherit_owner;
>> >+ break;
>> > default:
>> > r = -ENOIOCTLCMD;
>> > break;
>> >diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
>> >index b95dd84eef2d..1e192038633d 100644
>> >--- a/include/uapi/linux/vhost.h
>> >+++ b/include/uapi/linux/vhost.h
>> >@@ -235,4 +235,6 @@
>> > */
>> > #define VHOST_VDPA_GET_VRING_SIZE _IOWR(VHOST_VIRTIO, 0x82, \
>> > struct vhost_vring_state)
>> >+
>>
>> Please add a documentation here, this is UAPI, so the user should
>> know what this ioctl does based on the parameter.
>>
>> Thanks,
>> Stefano
>>
>> >+#define VHOST_SET_INHERIT_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, bool)
>> > #endif
>> >--
>> >2.45.0
>> >
>>
>
Powered by blists - more mailing lists