Re: [Qemu-devel] [PATCH v2] linux-user/mmap.c: Avoid choosing NULL as start address

[Richard Henderson]

On 01/06/2018 05:01 PM, Maximilian Riemensberger wrote:
> mmap() is required by the linux kernel ABI and POSIX to return a
> non-NULL address when the implementation chooses a start address for the
> mapping.
> 
> The current implementation of mmap_find_vma_reserved() can return NULL
> as start address of a mapping which leads to subsequent crashes inside
> the guests glibc, e.g. output of qemu-arm-static --strace executing a
> test binary stx_test:
> 
>     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.
> 
> This patch fixes mmap_find_vma_reserved() by skipping NULL as start
> address while searching for a suitable mapping start address.
> 
> CC: Riku Voipio <address@hidden>
> CC: Laurent Vivier <address@hidden>
> CC: Peter Maydell <address@hidden>
> Signed-off-by: Maximilian Riemensberger <address@hidden>
> ---
> Changes since v1:
>     - Applied feedback from Laurent Vivier

Reviewed-by: Richard Henderson <address@hidden>


r~