Messages in this thread | | | From | Dmitry Vyukov <> | Date | Mon, 25 Feb 2019 13:01:08 +0100 | Subject | Re: [PATCH] kasan: prevent recursive instrumentation |
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On Mon, Feb 25, 2019 at 12:35 PM Mark Rutland <mark.rutland@arm.com> wrote: > > On Sat, Feb 23, 2019 at 11:29:45AM +0100, Dmitry Vyukov wrote: > > On Fri, Feb 22, 2019 at 7:29 PM Mark Rutland <mark.rutland@arm.com> wrote: > > > > > > When CONFIG_KASAN is selected, <linux/kasan-checks.h> defines the > > > prototypes for kasan_check_{read,write}(), rather than inline stubs. > > > > +kasan-dev@googlegroups.com > > > > Doesn't this do the same as? > > https://groups.google.com/d/msg/kasan-dev/NwEdpGgUeac/oXUIRUC6CAAJ > > I had missed that patch -- thanks for the pointer! > > Either patch should both fix the issue with the EFI stub, but the > __kasan_check*() renaming in this patch also prevents unexpected > instrumentation within mm/kasan/common.c, if a call to kasan_check_*() > were inlined there. > > If you think that robustness is worthwhile, I can spin a v2 making that > a bit clearer, and fix the logic to look at __SANITIZE_ADDRESS__ rather > than adding the KASAN_NOSANITIZE definition. > > AFAICT Arnd's patch isn't queued anywhere just yet.
I dunno. I don't have strong preference. Also not sure if Arnd's patch is not, say, in mm... problems of extremely long patch submission times... patches should take at most days to commit.
> > > This is the case even when it is included by files which are not > > > instrumented by KASAN. Where helpers (e.g. the atomics) are instrumented > > > with explicit calls to kasan_check_{read,write}(), this results in files > > > being unexpectedly instrumented. > > > > > > This is problematic as it can result in instrumentation in files which > > > cannot safely call these functions, such as within the EFI stub: > > > > > > [mark@lakrids:~/src/linux]% usekorg 8.1.0 make ARCH=arm64 CROSS_COMPILE=aarch64-linux- -j64 -s > > > drivers/firmware/efi/libstub/arm-stub.stub.o: In function `atomic_set': > > > /home/mark/src/linux/./include/asm-generic/atomic-instrumented.h:44: undefined reference to `__efistub_kasan_check_write' > > > /home/mark/src/linux/./include/asm-generic/atomic-instrumented.h:44:(.init.text+0xa0): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `__efistub_kasan_check_write' > > > Makefile:1021: recipe for target 'vmlinux' failed > > > make: *** [vmlinux] Error 1 > > > > > > Let's avoid this by ensuring that uninstrumented files are given the > > > same stub definition of these functions used for !KASAN builds. So that > > > the stub defintions don't conflict with the real definitions in > > > (uninstrumented) common KASAN code, the real definitions are prefixed > > > with underscores, and called from unprefixed macros. > > > > > > Any compiler-generated instrumentation uses separate > > > __asan_{load,store}_*() entry points, and is not affected by this > > > change. > > > > > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > > > Cc: Alexander Potapenko <glider@google.com> > > > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > > > Cc: Dmitry Vyukov <dvyukov@google.com> > > > Cc: Ingo Molnar <mingo@kernel.org> > > > --- > > > include/linux/kasan-checks.h | 8 +++++--- > > > mm/kasan/common.c | 8 ++++---- > > > scripts/Makefile.kasan | 2 +- > > > 3 files changed, 10 insertions(+), 8 deletions(-) > > > > > > Hi, > > > > > > Assuming the KASAN folk are happy with this, I'd like this to be queued in the > > > tip tree, where the arm64 instrumented atomics are already queued. > > > > > > Thanks, > > > Mark. > > > > > > diff --git a/include/linux/kasan-checks.h b/include/linux/kasan-checks.h > > > index d314150658a4..6cf4b41a5393 100644 > > > --- a/include/linux/kasan-checks.h > > > +++ b/include/linux/kasan-checks.h > > > @@ -2,9 +2,11 @@ > > > #ifndef _LINUX_KASAN_CHECKS_H > > > #define _LINUX_KASAN_CHECKS_H > > > > > > -#ifdef CONFIG_KASAN > > > -void kasan_check_read(const volatile void *p, unsigned int size); > > > -void kasan_check_write(const volatile void *p, unsigned int size); > > > +#if defined(CONFIG_KASAN) && !defined (KASAN_NOSANITIZE) > > > +void __kasan_check_read(const volatile void *p, unsigned int size); > > > +#define kasan_check_read __kasan_check_read > > > +void __kasan_check_write(const volatile void *p, unsigned int size); > > > +#define kasan_check_write __kasan_check_write > > > #else > > > static inline void kasan_check_read(const volatile void *p, unsigned int size) > > > { } > > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > > > index 73c9cbfdedf4..630e32838adb 100644 > > > --- a/mm/kasan/common.c > > > +++ b/mm/kasan/common.c > > > @@ -95,17 +95,17 @@ void kasan_disable_current(void) > > > current->kasan_depth--; > > > } > > > > > > -void kasan_check_read(const volatile void *p, unsigned int size) > > > +void __kasan_check_read(const volatile void *p, unsigned int size) > > > { > > > check_memory_region((unsigned long)p, size, false, _RET_IP_); > > > } > > > -EXPORT_SYMBOL(kasan_check_read); > > > +EXPORT_SYMBOL(__kasan_check_read); > > > > > > -void kasan_check_write(const volatile void *p, unsigned int size) > > > +void __kasan_check_write(const volatile void *p, unsigned int size) > > > { > > > check_memory_region((unsigned long)p, size, true, _RET_IP_); > > > } > > > -EXPORT_SYMBOL(kasan_check_write); > > > +EXPORT_SYMBOL(__kasan_check_write); > > > > > > #undef memset > > > void *memset(void *addr, int c, size_t len) > > > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan > > > index 25c259df8ffa..c475a8ac776c 100644 > > > --- a/scripts/Makefile.kasan > > > +++ b/scripts/Makefile.kasan > > > @@ -52,5 +52,5 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \ > > > endif # CONFIG_KASAN_SW_TAGS > > > > > > ifdef CONFIG_KASAN > > > -CFLAGS_KASAN_NOSANITIZE := -fno-builtin > > > +CFLAGS_KASAN_NOSANITIZE := -fno-builtin -DKASAN_NOSANITIZE > > > endif > > > -- > > > 2.11.0 > > >
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