Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1211874

Re: [x86] copy_from{to}_user question

Show all headers | View raw

> On Aug 22, 2015, at 17:05, Borislav Petkov <bp@suse.de> wrote:
> 
> On Fri, Aug 21, 2015 at 02:06:16PM -0700, H. Peter Anvin wrote:
>> What I'm saying is that we do do STAC, which *disables* SMAP.  We have
>> to do that because one pointer is known to be a user space pointer.
>> 
>> However, we currently don't verify that the *other* pointer is kernel
>> space, which it is supposed to be (if not, we should be using
>> copy_in_user).  We have to do this manually since we have to STAC which
>> means SMAP doesn't do anything at all.  I believe it would be a good
>> idea to add such checks (and they would even benefit non-SMAP hardware.)
> 
> Ah, ok, so we're on the same page.
> 
> And yep, Linus gave the probe_kernel_read() suggestion in another mail.
> 
i am not clear about what is STAC / SMAP ?
could you give me a link for understanding ?

Linus suggest to use probe_kernel_read() , but also said it is 
not efficient to use it, because we need copy the data 2 times by this method.

my patch suggests to use copy_in_user() ,
but seems not a generic(portable) function on all architectures.

Thanks--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [x86] copy_from{to}_user question "H. Peter Anvin" <hpa@zytor.com> - 2015-08-20 20:30 +0200
  Re: [x86] copy_from{to}_user question Borislav Petkov <bp@suse.de> - 2015-08-21 06:40 +0200
    Re: [x86] copy_from{to}_user question "H. Peter Anvin" <hpa@zytor.com> - 2015-08-21 23:10 +0200
      Re: [x86] copy_from{to}_user question Borislav Petkov <bp@suse.de> - 2015-08-22 11:10 +0200
        Re: [x86] copy_from{to}_user question yalin wang <yalin.wang2010@gmail.com> - 2015-08-24 10:00 +0200
          Re: [x86] copy_from{to}_user question Jeff Epler <jepler@unpythonic.net> - 2015-08-24 14:10 +0200

csiph-web