lkml.org 
[lkml]   [2019]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 09/20] 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.

    Cc: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    mm/kasan/Makefile | 3 +++
    mm/kasan/common.c | 10 ++++++++++
    mm/kasan/report.c | 3 +--
    3 files changed, 14 insertions(+), 2 deletions(-)

    --- 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
    --- a/mm/kasan/common.c
    +++ b/mm/kasan/common.c
    @@ -34,6 +34,7 @@
    #include <linux/types.h>
    #include <linux/vmalloc.h>
    #include <linux/bug.h>
    +#include <linux/uaccess.h>

    #include "kasan.h"
    #include "../slab.h"
    @@ -612,6 +613,15 @@ void kasan_free_shadow(const struct vm_s
    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)
    {
    --- a/mm/kasan/report.c
    +++ b/mm/kasan/report.c
    @@ -281,8 +281,7 @@ void kasan_report_invalid_free(void *obj
    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;

    \
     
     \ /
      Last update: 2019-03-07 12:55    [W:2.801 / U:0.080 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site