[PATCH 4.14 002/124] powerpc/64/module: REL32 relocation range check

Greg Kroah-Hartman
2018-11-19T16:47:39Z

From: Nicholas Piggin <npiggin@gmail.com>

[ Upstream commit b851ba02a6f3075f0f99c60c4bc30a4af80cf428 ]

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!

Possibly other relocations (ADDR32, REL16, TOC16, etc.) should also have
overflow checks.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/kernel/module_64.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -656,7 +656,14 @@ int apply_relocate_add(Elf64_Shdr *sechd

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: