Re: [Qemu-devel] linux-user/mmap: Should not return NULL on guest call mmap(NULL, ...), causes crash inside glibc

[Maximilian Riemensberger]

On 05.01.18 22:13, Maximilian Riemensberger wrote:
> On 05.01.18 19:38, Peter Maydell wrote:
>> On 5 January 2018 at 18:13, Maximilian Riemensberger
>> <address@hidden> wrote:
>>> Hi,
>>>
>>> yesterday I hit the following problem when running an arm linux executable 
>>> on
>>> qemu-2.10 (qemu-arm-static through binfmt_misc)
>>>
>>> 1879 
>>> mmap2(NULL,8388608,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS|0x20000,-1,0)
>>>  = 0x00000000
>>> 1879 write(2,0xf6fd39d0,79) stx_test: allocatestack.c:514: allocate_stack: 
>>> Assertion `mem != NULL' failed.
>>>
>>> The issue comes up when the executable creates and joins lots of
>>> threads in a loop (it's a unit test).  Eventually, glibc allocatestack
>>> hits the mmap(NULL, ...) == NULL.  Judging from the posix and linux
>>> manuals mmap(NULL, ...) never returns NULL.  Either it fails with MAP_FAILED
>>> or it succeeds and returns non-NULL address.
>>
>> Given the heavy use of threading, can you retest with QEMU 2.11,
>> please? We fixed a couple of threading issues in linux-user there.
> 
> Same error with fresh qemu-2.11 build.

I just sent out a online patch that fixes the issue for me.

Cheers
        Max