Richard Henderson <richard.hender...@linaro.org> writes:
> Use this as extra protection for the guest mapping over
> any qemu host mappings.
>
> Tested-by: Helge Deller <del...@gmx.de>
> Reviewed-by: Helge Deller <del...@gmx.de>
> Reviewed-by: Akihiko Odaki <akihiko.od...@daynix.com>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> linux-user/elfload.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 36e4026f05..1b4bb2d5af 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -3147,8 +3147,11 @@ static void load_elf_image(const char *image_name, int
> image_fd,
> /*
> * Reserve address space for all of this.
> *
> - * In the case of ET_EXEC, we supply MAP_FIXED so that we get
> - * exactly the address range that is required.
> + * In the case of ET_EXEC, we supply MAP_FIXED_NOREPLACE so that we get
> + * exactly the address range that is required. Without reserved_va,
> + * the guest address space is not isolated. We have attempted to avoid
> + * conflict with the host program itself via probe_guest_base, but using
> + * MAP_FIXED_NOREPLACE instead of MAP_FIXED provides an extra check.
> *
> * Otherwise this is ET_DYN, and we are searching for a location
> * that can hold the memory space required. If the image is
> @@ -3160,7 +3163,7 @@ static void load_elf_image(const char *image_name, int
> image_fd,
> */
> load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_NONE,
> MAP_PRIVATE | MAP_ANON | MAP_NORESERVE |
> - (ehdr->e_type == ET_EXEC ? MAP_FIXED : 0),
> + (ehdr->e_type == ET_EXEC ? MAP_FIXED_NOREPLACE :
> 0),
> -1, 0);
We should probably also check the result == load_addr for the places
where MAP_FIXED_NOREPLACE isn't supported as we have this in osdep.h:
#ifndef MAP_FIXED_NOREPLACE
#define MAP_FIXED_NOREPLACE 0
#endif
See 2667e069e7 (linux-user: don't use MAP_FIXED in pgd_find_hole_fallback)
> if (load_addr == -1) {
> goto exit_mmap;
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
