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authorMichael Neuling <mikey@neuling.org>2018-09-14 11:14:11 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2018-09-18 22:42:54 +1000
commit51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 (patch)
treeb11eefccbfe4df8cc01511fb81b7caf7a23d790e /arch
parentf14040bca89258b8a1c71e2112e430462172ce93 (diff)
powerpc: Avoid code patching freed init sections
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. Cc: stable@vger.kernel.org # 4.13+ Signed-off-by: Michael Neuling <mikey@neuling.org> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/include/asm/setup.h1
-rw-r--r--arch/powerpc/lib/code-patching.c6
-rw-r--r--arch/powerpc/mm/mem.c2
3 files changed, 9 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index 1a951b00465d..1fffbba8d6a5 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -9,6 +9,7 @@ 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 850f3b8f4da5..6ae2777c220d 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -28,6 +28,12 @@ static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
{
int err;
+ /* Make sure we aren't patching a freed init section */
+ if (init_mem_is_free && init_section_contains(exec_addr, 4)) {
+ pr_debug("Skipping init section patching addr: 0x%px\n", exec_addr);
+ return 0;
+ }
+
__put_user_size(instr, patch_addr, 4, err);
if (err)
return err;
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 5c8530d0c611..04ccb274a620 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -63,6 +63,7 @@
#endif
unsigned long long memory_limit;
+bool init_mem_is_free;
#ifdef CONFIG_HIGHMEM
pte_t *kmap_pte;
@@ -396,6 +397,7 @@ void free_initmem(void)
{
ppc_md.progress = ppc_printk_progress;
mark_initmem_nx();
+ init_mem_is_free = true;
free_initmem_default(POISON_FREE_INITMEM);
}