The recent module relocation overflow crash demonstrated that we
have no range checking on REL32 relative relocations. This patch
implements a basic check, the same kernel that previously oopsed
and rebooted now continues with some of these errors when loading
the module:
module_64: x_tables: REL32 527703503449812 out of range!
Question is whether other relocations (ADDR32, REL16, TOC16, etc.)
should also have overflow checks.
---
arch/powerpc/kernel/module_64.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index a2636c250b7b..2a2fb656d23b 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -678,7 +678,14 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
case R_PPC64_REL32:
/* 32 bits relative (used by relative exception tables)
*/
- *(u32 *)location = value - (unsigned long)location;
+ /* Convert value to relative */
+ value -= (unsigned long)location;
+ if (value + 0x80000000 > 0xffffffff) {
+ pr_err("%s: REL32 %li out of range!\n",
+ me->name, (long int)value);
+ return -ENOEXEC;
+ }
+ *(u32 *)location = value;
break;
case R_PPC64_TOCSAVE:
--
2.18.0
