Re: [PATCH] livepatch: x86: bugfix about kASLR

From: Cyril B.
Date: Wed Nov 04 2015 - 11:59:14 EST

Zhou Chengming wrote:
When enable KASLR, func->old_addr will be set to zero
and livepatch will find the right old address.
But for reloc, livepatch just verify it using reloc->val
(old addr from user), so verify failed and report
"kernel mismatch" error.

Reported-by: Cyril B.<cbay@xxxxxxxxxxxxxx>
Signed-off-by: Zhou Chengming<zhouchengming1@xxxxxxxxxx>
kernel/livepatch/core.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 53196e2..c8885c6 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -311,7 +311,12 @@ static int klp_write_object_relocations(struct module *pmod,
return -EINVAL;

for (reloc = obj->relocs; reloc->name; reloc++) {
- if (!klp_is_module(obj)) {
+ /* KASLR is enabled, disregard old_addr from user */
+ reloc->val = 0;
+ if (reloc->val&& !klp_is_module(obj)) {
ret = klp_verify_vmlinux_symbol(reloc->name,
if (ret)

I still get the 'symbol not found in symbol table' error with that patch (on top of Linux 4.3).

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