OpenE2K/linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

powerpc: Avoid code patching freed init sections

Browse Source 
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>
This commit is contained in:
Michael Neuling 2018-09-14 11:14:11 +10:00 committed by Michael Ellerman
parent f14040bca8
commit 51c3c62b58
3 changed files with 9 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/setup.h
View File

@ -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);

6
arch/powerpc/lib/code-patching.c
View File

@ -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;

2
arch/powerpc/mm/mem.c
View File

@ -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);
}