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authorPeter Zijlstra <peterz@infradead.org>2019-04-03 09:39:50 +0200
committerIngo Molnar <mingo@kernel.org>2019-04-03 11:02:24 +0200
commit57b78a62e7f23c4686fe54091cdc3d12e60d6513 (patch)
treed8ac655da75b7a72365c7226b93e78c06d0c9204 /mm/kasan
parenta936af8ea3580855adcc80daa8e01c0196afeb15 (diff)
x86/uaccess, kasan: Fix KASAN vs SMAP
KASAN inserts extra code for every LOAD/STORE emitted by te compiler. Much of this code is simple and safe to run with AC=1, however the kasan_report() function, called on error, is most certainly not safe to call with AC=1. Therefore wrap kasan_report() in user_access_{save,restore}; which for x86 SMAP, saves/restores EFLAGS and clears AC before calling the real function. Also ensure all the functions are without __fentry__ hook. The function tracer is also not safe. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'mm/kasan')
-rw-r--r--mm/kasan/Makefile3
-rw-r--r--mm/kasan/common.c10
-rw-r--r--mm/kasan/report.c3
3 files changed, 14 insertions, 2 deletions
diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 5d1065efbd47..613dfe681e9f 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -2,11 +2,13 @@
KASAN_SANITIZE := n
UBSAN_SANITIZE_common.o := n
UBSAN_SANITIZE_generic.o := n
+UBSAN_SANITIZE_generic_report.o := n
UBSAN_SANITIZE_tags.o := n
KCOV_INSTRUMENT := n
CFLAGS_REMOVE_common.o = -pg
CFLAGS_REMOVE_generic.o = -pg
+CFLAGS_REMOVE_generic_report.o = -pg
CFLAGS_REMOVE_tags.o = -pg
# Function splitter causes unnecessary splits in __asan_load1/__asan_store1
@@ -14,6 +16,7 @@ CFLAGS_REMOVE_tags.o = -pg
CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
obj-$(CONFIG_KASAN) := common.o init.o report.o
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 80bbe62b16cd..09c586474511 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -36,6 +36,7 @@
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/bug.h>
+#include <linux/uaccess.h>
#include "kasan.h"
#include "../slab.h"
@@ -614,6 +615,15 @@ void kasan_free_shadow(const struct vm_struct *vm)
vfree(kasan_mem_to_shadow(vm->addr));
}
+extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
+
+void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
+{
+ unsigned long flags = user_access_save();
+ __kasan_report(addr, size, is_write, ip);
+ user_access_restore(flags);
+}
+
#ifdef CONFIG_MEMORY_HOTPLUG
static bool shadow_mapped(unsigned long addr)
{
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index ca9418fe9232..0772820ad098 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -281,8 +281,7 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
end_report(&flags);
}
-void kasan_report(unsigned long addr, size_t size,
- bool is_write, unsigned long ip)
+void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
{
struct kasan_access_info info;
void *tagged_addr;