Re: [Qemu-devel] [PATCH v2 2/2] linux-user: allocate heap memory for execve arguments

[Eric Blake]

On 03/06/2017 09:53 AM, Eric Blake wrote:
> On 03/06/2017 01:17 AM, P J P wrote:
>> From: Prasad J Pandit <address@hidden>
>>
>> Arguments passed to execve(2) call from user program could
>> be large, allocating stack memory for them via alloca(3) call
>> would lead to bad behaviour. Use 'g_malloc0' to allocate memory
>> for such arguments.
>>
>> Signed-off-by: Prasad J Pandit <address@hidden>
>> ---
>>  linux-user/syscall.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> Is this patch alone (without 1/2) sufficient to solve the problem?  If
> so, then drop 1/2.
> 
>>
>> Update per: replace alloca() with g_malloc0()
>>   -> https://lists.gnu.org/archive/html/qemu-devel/2017-03/msg00750.html
>>
>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>> index 86a4a9c..404fb0b 100644
>> --- a/linux-user/syscall.c
>> +++ b/linux-user/syscall.c
>> @@ -7800,8 +7800,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
>> arg1,
> 
> What version of qemu are you patching?  Line 7800 of current master is
> nowhere near 'case TARGET_NR_execve:' (line 7899)
> 
>>                  ret = -TARGET_E2BIG;
>>                  break;
>>              }
> 
> and current master has 'goto efault' rather than directly setting ret at
> this point.

Okay, I see that this context came from patch 1/2. Sorry for the noise
(I was trying to review this patch in isolation, since I've already
argued that 1/2 is probably not necessary).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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