On 2021/6/16 15:11, Suren Baghdasaryan wrote:

On Tue, Jun 15, 2021 at 11:52 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:

...

On Wed, Jun 16, 2021 at 02:47:15PM +0800, Liu Shixin wrote:

...

Hi, Suren,

I read the previous discussion about fixing CVE-2020-29374 in stable 4.14 and 4.19 in https://lore.kernel.org/linux-mm/20210401181741.168763-1-surenb@google.com/

https://lore.kernel.org/linux-mm/20210401181741.168763-1-surenb@google.com/

And the results of the discussion is that you backports of 17839856fd58 for 4.14 and

4.19 kernels.

But the bug about dax and strace in the discussion has not been solved, right? I don't

find a conclusion on this issue, am I missing something? Does this problem still exist in

the stable 4.14 and 4.19 kernel?

That is my understanding after discussions with Andrea but I did not verify that myself. As Greg pointed out, the best way would be to try it out. Thanks, Suren.

...

As the code is all there for you, can you just test them and see for yourself?

thanks,

greg k-h

.

Thank you both for replies. I have tested it in stable 4.19 kernel and the bug is existed as expected.

Thanks, Liu Shixin

On 6/16/21 11:36 AM, Greg Kroah-Hartman wrote:

On Wed, Jun 16, 2021 at 05:28:54PM +0800, Liu Shixin wrote:

...

On 2021/6/16 15:11, Suren Baghdasaryan wrote:

...

On Tue, Jun 15, 2021 at 11:52 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:

...

On Wed, Jun 16, 2021 at 02:47:15PM +0800, Liu Shixin wrote:

...

Hi, Suren,

I read the previous discussion about fixing CVE-2020-29374 in stable 4.14 and 4.19 in https://lore.kernel.org/linux-mm/20210401181741.168763-1-surenb@google.com/

https://lore.kernel.org/linux-mm/20210401181741.168763-1-surenb@google.com/

And the results of the discussion is that you backports of 17839856fd58 for 4.14 and

4.19 kernels.

But the bug about dax and strace in the discussion has not been solved, right? I don't

find a conclusion on this issue, am I missing something? Does this problem still exist in

the stable 4.14 and 4.19 kernel?

That is my understanding after discussions with Andrea but I did not verify that myself. As Greg pointed out, the best way would be to try it out. Thanks, Suren.

...

As the code is all there for you, can you just test them and see for yourself?

thanks,

greg k-h

.

Thank you both for replies. I have tested it in stable 4.19 kernel and the bug is existed as expected.

If you can reproduce it, great. That means a root cause can be found and fixed, hopefully in a minimal way.

Great, can you provide a working backport of the patches needed to solve this for 4.19 so that we can apply them?

We probably don't want to blindly backport the upstream patches (that also fixed dax+ptrace as a side-effect) because they changed the semantics a lot and led to further fixes, which is IMHO too risky to do now in stable. Linus also thought so:

https://lore.kernel.org/linux-mm/CAHk-=whUKYdWbKfFzXXnK8n04oCMwEgSnG8Y3tgE=Y...

thanks,

greg k-h