From: Michael Neuling <mikey@xxxxxxxxxxx>
commit 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 upstream.
This stops us from doing code patching in init sections after they've
been freed.
In this chain:
kvm_guest_init() ->
kvm_use_magic_page() ->
fault_in_pages_readable() ->
__get_user() ->
__get_user_nocheck() ->
barrier_nospec();
We have a code patching location at barrier_nospec() and
kvm_guest_init() is an init function. This whole chain gets inlined,
so when we free the init section (hence kvm_guest_init()), this code
goes away and hence should no longer be patched.
We seen this as userspace memory corruption when using a memory
checker while doing partition migration testing on powervm (this
starts the code patching post migration via
/sys/kernel/mobility/migration). In theory, it could also happen when
using /sys/kernel/debug/powerpc/barrier_nospec.
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/setup.h | 1 +
arch/powerpc/lib/code-patching.c | 13 +++++++++++++
arch/powerpc/mm/mem.c | 2 ++
3 files changed, 16 insertions(+)
diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index ca6f8713e7ad..21daee862399 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -8,6 +8,7 @@ extern void ppc_printk_progress(char *s, unsigned short hex);
extern unsigned int rtas_data;
extern unsigned long long memory_limit;
+extern bool init_mem_is_free;
extern unsigned long klimit;
extern void *zalloc_maybe_bootmem(size_t size, gfp_t mask);
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 2ce6159d8983..570c06a00db6 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -14,12 +14,25 @@
#include <asm/page.h>
#include <asm/code-patching.h>
#include <asm/uaccess.h>
+#include <asm/setup.h>
+#include <asm/sections.h>
+static inline bool is_init(unsigned int *addr)
+{
+ return addr >= (unsigned int *)__init_begin && addr < (unsigned int *)__init_end;
+}
+
int patch_instruction(unsigned int *addr, unsigned int instr)
{
int err;
+ /* Make sure we aren't patching a freed init section */
+ if (init_mem_is_free && is_init(addr)) {
+ pr_debug("Skipping init section patching addr: 0x%px\n", addr);
+ return 0;
+ }
+
__put_user_size(instr, addr, 4, err);
if (err)
return err;
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 22d94c3e6fc4..1efe5ca5c3bc 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -62,6 +62,7 @@
#endif
unsigned long long memory_limit;
+bool init_mem_is_free;
#ifdef CONFIG_HIGHMEM
pte_t *kmap_pte;
@@ -381,6 +382,7 @@ void __init mem_init(void)
void free_initmem(void)
{
ppc_md.progress = ppc_printk_progress;
+ init_mem_is_free = true;
free_initmem_default(POISON_FREE_INITMEM);
}
--
2.20.1
