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[PATCH] linux-user/elfload: fix address calculation in fallback scenario
From: |
Vincent Fazio |
Subject: |
[PATCH] linux-user/elfload: fix address calculation in fallback scenario |
Date: |
Sun, 31 Jan 2021 00:19:48 -0600 |
From: Vincent Fazio <vfazio@gmail.com>
Previously, guest_loaddr was not taken into account when returning an
address from pgb_find_hole when /proc/self/maps was unavailable which
caused an improper guest_base address to be calculated.
This could cause a SIGSEGV later in load_elf_image -> target_mmap for
ET_EXEC type images since the mmap MAP_FIXED flag is specified which
could clobber existing mappings at the address returnd by g2h().
mmap(0xd87000, 16846912, PROT_NONE,
MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE|0x100000, -1, 0) = 0xd87000
munmap(0xd87000, 16846912) = 0
write(2, "Locating guest address space @ 0"..., 40Locating guest address
space @ 0xd87000) = 40
mmap(0x1187000, 16850944, PROT_NONE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x1187000
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x2188310} ---
+++ killed by SIGSEGV +++
Now, pgd_find_hole accounts for guest_loaddr in this scenario.
Fixes: ad592e37dfcc ("linux-user: provide fallback pgd_find_hole for bare
chroots")
Signed-off-by: Vincent Fazio <vfazio@gmail.com>
---
linux-user/elfload.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 8d425f9ed0..6d606b9442 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2242,7 +2242,8 @@ static uintptr_t pgb_find_hole(uintptr_t guest_loaddr,
uintptr_t guest_size,
brk = (uintptr_t)sbrk(0);
if (!maps) {
- return pgd_find_hole_fallback(guest_size, brk, align, offset);
+ ret = pgd_find_hole_fallback(guest_size, brk, align, offset);
+ return ret - guest_loaddr;
}
/* The first hole is before the first map entry. */
--
2.30.0
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