Re: [uml-devel] [PATCH] um: pass siginfo to guest process

[Richard Weinberger <richard@nod.at>]

[-- Attachment #1.1: Type: text/plain, Size: 1486 bytes --]

Am 07.06.2012 23:39, schrieb Martin Pärtel:
> On 06/08/2012 12:26 AM, Richard Weinberger wrote:
> 
>> Am 07.06.2012 22:59, schrieb Martin Pärtel:
>>> Signal handlers in UML guest processes now get correct siginfo_t fields
>>> for SIGTRAP, SIGFPE, SIGILL and SIGBUS. Specifically, si_addr and si_code
>>> are now correct where previously they were si_addr = NULL and si_code = 128.
>>
>> What exactly is broken?
>> In my SIGSEGV test case si_addr is not NULL, it contains the correct faulting address.
>>
> 
> 
> SIGSEGV is probably fine. At least SIGFPE is not. Test program below.
> 
>>> +
>>> +            ptrace(PTRACE_GETSIGINFO, pid, 0,&si);
>>> +
>>
>> Doesn't this leak the host siginfo_t into the guest?
>>
> 
> 
> Docs for PTRACE_GETSIGINFO say `si' gets a copy. After that, `si' is not used for anything other than giving it to the guest. But I really can't say I
> understand the surrounding code too well so please review carefully :)

I was not talking about a memory leak.
What I meant was a information leak.
Using the host siginfo_t a guest process may get it's UID, PID, memory location, etc... on the host side.

Anyway, thanks for the test case!
This seems to be really broken.
I had only a few minutes to look at the issue but I think the correct way to fix is changing
arch/um/kernel/trap.c:relay_signal() to use force_sig_info() instead of force_sig().
Create siginfo_t and fill by hand like segv() does.

Thanks,
//richard


[-- Attachment #1.2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 490 bytes --]

[-- Attachment #2: Type: text/plain, Size: 395 bytes --]

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/

[-- Attachment #3: Type: text/plain, Size: 194 bytes --]

_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel