From 7fe905d0973eee071ebc4861cd6d23138116cd9e Mon Sep 17 00:00:00 2001 From: Michael Neuling Date: Mon, 22 Apr 2019 00:20:29 +1000 Subject: powerpc: Avoid code patching freed init sections 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 Reviewed-by: Nicholas Piggin Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/lib/code-patching.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'arch/powerpc/lib/code-patching.c') 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 #include #include +#include +#include +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; -- cgit v1.2.3