[CRIU] [PATCH 17/20] compel handle_elf(): fix strings sect bounds check

[Kir Kolyshkin]

Got this when using compel hgen on arm 32-bit:

Error (compel/src/lib/handle-elf-host.c:115): String section header
@0xf66e11ec is out of [0xf66e1174, 0xf66e1264)

Looking at this, it does not make sense. For the reference,
sizeof(Elf_Shdr) is 0x28, so end position is also well within bounds.

Apparently, the check for string section header bounds is wrong
as the last argument of __ptr_struct_oob() is supposed to be a
region size, not the region end address as it is.

This always worked before because the check was too relaxed, and
compel was never used on 32-bit ARM. This time it didn't work
because of a 32-bit overflow, which helped to find this bug.

This is a fix to commit 6402f03 ("compel: separate get_strings_section
from __handle_elf").

Cc: Dmitry Safonov <dsafonov at virtuozzo.com>
Signed-off-by: Kir Kolyshkin <kir at openvz.org>
---
 compel/src/lib/handle-elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compel/src/lib/handle-elf.c b/compel/src/lib/handle-elf.c
index 14b066b..035cd0d 100644
--- a/compel/src/lib/handle-elf.c
+++ b/compel/src/lib/handle-elf.c
@@ -110,7 +110,7 @@ static const char *get_strings_section(Elf_Ehdr *hdr, uintptr_t mem, size_t size
 	 */
 	addr = sec_table + ((size_t) hdr->e_shentsize) * hdr->e_shstrndx;
 	if (__ptr_struct_oob(addr, sizeof(Elf_Shdr),
-			sec_table, sec_table + sec_table_size)) {
+			sec_table, sec_table_size)) {
 		pr_err("String section header @%#zx is out of [%#zx, %#zx)\n",
 			addr, sec_table, sec_table + sec_table_size);
 		return NULL;
-- 
2.7.4