From: Luke Shumaker <luke...@parabola.nu>
init_guest_commpage needs to check if the mapped space, which ends at
real_start+real_size overlaps with where it needs to put the commpage,
which is (assuming sane qemu_host_page_size) guest_base + 0xffff000, where
guest_base is real_start - guest_start.
[guest_base][ 0xffff0000 ][commpage]
[guest_base][guest_start][real_size] [commpage]
[ real_start ][real_size] [commpage]
^
fail if this gap < 0
Since init_guest_commpage wants to do everything relative to guest_base
(rather than real_start), it obviously needs to be comparing 0xffff0000
against guest_start+real_size, not just real_size.
This bug has been present since 806d102141b99d4f1e55a97d68b7ea8c8ba3129f in
2012, but guest_start is usually 0, and prior to v2.11 real_size was
usually much smaller than 0xffff0000, so it was uncommon for it to have
made a difference.
Signed-off-by: Luke Shumaker <luke...@parabola.nu>
Message-Id: <20171228180814.9749-5-luke...@lukeshu.com>
Reviewed-by: Peter Maydell <peter.mayd...@linaro.org>
Signed-off-by: Laurent Vivier <laur...@vivier.eu>
---
linux-user/elfload.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index dcdd756908..feecbd4163 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1856,7 +1856,7 @@ unsigned long init_guest_space(unsigned long host_start,
#if defined(TARGET_ARM) && !defined(TARGET_AARCH64)
/* On 32-bit ARM, we need to also be able to map the commpage. */
int valid = init_guest_commpage(real_start - guest_start,
- real_size);
+ real_size + guest_start);
if (valid == 1) {
break;
} else if (valid == -1) {
--
2.14.3
