diff mbox series

[v8,11/17] linux-user: Use MAP_FIXED_NOREPLACE for initial image mmap

Message ID 20230804014517.6361-12-richard.henderson@linaro.org
State Superseded
Headers show
Series linux-user: brk fixes | expand

Commit Message

Richard Henderson Aug. 4, 2023, 1:45 a.m. UTC 
Use this as extra protection for the guest mapping over
any qemu host mappings.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/elfload.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

Akihiko Odaki Aug. 4, 2023, 5:22 a.m. UTC | #1 
On 2023/08/04 10:45, Richard Henderson wrote:
> Use this as extra protection for the guest mapping over
> any qemu host mappings.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Helge Deller Aug. 4, 2023, 10:18 a.m. UTC | #2 
* Richard Henderson <richard.henderson@linaro.org>:
> Use this as extra protection for the guest mapping over
> any qemu host mappings.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Helge Deller <deller@gmx.de>
diff mbox series

Patch

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 2aee2298ec..0c64aad8a5 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -3146,8 +3146,11 @@  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
@@ -3159,7 +3162,7 @@  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);
     if (load_addr == -1) {
         goto exit_mmap;