From 1c38a84d45862be06ac418618981631eddbda741 Mon Sep 17 00:00:00 2001 From: Michael Neuling Date: Thu, 11 Apr 2019 21:45:59 +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. Cc: stable@vger.kernel.org # 4.13+ Signed-off-by: Michael Neuling Reviewed-by: Nicholas Piggin Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/lib/code-patching.c | 8 ++++++++ 1 file changed, 8 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 753d591f1b52..c77c486fbf24 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -14,12 +14,20 @@ #include #include #include +#include +#include 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 && init_section_contains(addr, 4)) { + 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 From 6482f0d6af10262ca6586327090a47f2feaf0fea Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Thu, 11 Apr 2019 21:46:13 +1000 Subject: powerpc/asm: Add a patch_site macro & helpers for patching instructions commit 06d0bbc6d0f56dacac3a79900e9a9a0d5972d818 upstream. Add a macro and some helper C functions for patching single asm instructions. The gas macro means we can do something like: 1: nop patch_site 1b, patch__foo Which is less visually distracting than defining a GLOBAL symbol at 1, and also doesn't pollute the symbol table which can confuse eg. perf. These are obviously similar to our existing feature sections, but are not automatically patched based on CPU/MMU features, rather they are designed to be manually patched by C code at some arbitrary point. Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/lib/code-patching.c | 16 ++++++++++++++++ 1 file changed, 16 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 c77c486fbf24..14535ad4cdd1 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -40,6 +40,22 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags) return patch_instruction(addr, create_branch(addr, target, flags)); } +int patch_branch_site(s32 *site, unsigned long target, int flags) +{ + unsigned int *addr; + + addr = (unsigned int *)((unsigned long)site + *site); + return patch_instruction(addr, create_branch(addr, target, flags)); +} + +int patch_instruction_site(s32 *site, unsigned int instr) +{ + unsigned int *addr; + + addr = (unsigned int *)((unsigned long)site + *site); + return patch_instruction(addr, instr); +} + unsigned int create_branch(const unsigned int *addr, unsigned long target, int flags) { -- cgit v1.2.3 From 48a5c81f3f1fc6470f1e39aea2effbfc9567abe5 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Mon, 1 Oct 2018 12:21:10 +0000 Subject: powerpc/lib: fix book3s/32 boot failure due to code patching commit b45ba4a51cde29b2939365ef0c07ad34c8321789 upstream. Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections") accesses 'init_mem_is_free' flag too early, before the kernel is relocated. This provokes early boot failure (before the console is active). As it is not necessary to do this verification that early, this patch moves the test into patch_instruction() instead of __patch_instruction(). This modification also has the advantage of avoiding unnecessary remappings. Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections") Cc: stable@vger.kernel.org # 4.13+ Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/lib/code-patching.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (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 14535ad4cdd1..c312955977ce 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -23,7 +23,7 @@ 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 && init_section_contains(addr, 4)) { + if (*PTRRELOC(&init_mem_is_free) && init_section_contains(addr, 4)) { pr_debug("Skipping init section patching addr: 0x%px\n", addr); return 0; } -- cgit v1.2.3