Re: [PATCH] gdbstub: Correct misparsing of vCont C/S requests

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Mon, 23 Nov 2020 at 13:41, Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>>
>> Peter Maydell <peter.maydell@linaro.org> writes:
>>
>> > In the vCont packet, two of the command actions (C and S) take an
>> > argument specifying the signal to be sent to the process/thread, which is
>> > sent as an ASCII string of two hex digits which immediately follow the
>> > 'C' or 'S' character.
>> >
>> > Our code for parsing this packet accidentally skipped the first of the
>> > two bytes of the signal value, because it started parsing the hex string
>> > at 'p + 1' when the preceding code had already moved past the 'C' or
>> > 'S' with "cur_action = *p++".
>> >
>> > This meant that we would only do the right thing for signals below
>> > 10, and would misinterpret the rest.  For instance, when the debugger
>> > wants to send the process a SIGPROF (27 on x86-64) we mangle this into
>> > a SIGSEGV (11).
>> >
>> > Remove the accidental double increment.
>> >
>> > Fixes: https://bugs.launchpad.net/qemu/+bug/1773743
>> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>>
>> LGTM
>>
>> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>>
>> > ---
>> > Haven't really given this enough testing to want to put it into 5.2,
>> > I think (though it does fix the repro in the bug report).
>> > The bug has been present since commit 544177ad1cfd78 from 2017.
>>
>> I'd be happy including it. I don't have any gdbstub patches queued at
>> the moment but I could put together one if you want or you could just
>> include it directly if you are now happy to.
>
> Now that 6.0 has opened up, I'll put this in via target-arm.next
> unless you'd prefer to take it.

Go for it, I have nothing else at the moment.

>
> -- PMM


-- 
Alex Bennée