(Albert's @google.com address is gone, removing it from CC list)
On Fri, Oct 23, 2020 at 10:16 AM Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> From: Albert van der Linde <alinde@xxxxxxxxxx>
>
> To test fault-tolerance of user memory acceses in x86, add support for
> fault injection.
>
> Make both put_user() and get_user() fail with -EFAULT, and clear_user()
> fail by not clearing any bytes.
>
> Reviewed-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
> Signed-off-by: Albert van der Linde <alinde@xxxxxxxxxx>
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
>
> ---
> v2:
> - no significant changes
>
> v3:
> - no changes
>
> v4:
> - instrument the new out-of-line implementations of get_user()/put_user()
> - fix a minor checkpatch warning in the inline assembly
>
> ---
> ---
> arch/x86/include/asm/uaccess.h | 36 ++++++++++++++++++++++------------
> arch/x86/lib/usercopy_64.c | 3 +++
> 2 files changed, 26 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index f13659523108..7041ebc48b75 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -5,6 +5,7 @@
> * User space memory access functions
> */
> #include <linux/compiler.h>
> +#include <linux/fault-inject-usercopy.h>
> #include <linux/kasan-checks.h>
> #include <linux/string.h>
> #include <asm/asm.h>
> @@ -126,11 +127,16 @@ extern int __get_user_bad(void);
> int __ret_gu; \
> register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX); \
> __chk_user_ptr(ptr); \
> - asm volatile("call __" #fn "_%P4" \
> - : "=a" (__ret_gu), "=r" (__val_gu), \
> - ASM_CALL_CONSTRAINT \
> - : "0" (ptr), "i" (sizeof(*(ptr)))); \
> - (x) = (__force __typeof__(*(ptr))) __val_gu; \
> + if (should_fail_usercopy()) { \
> + (x) = 0; \
> + __ret_gu = -EFAULT; \
> + } else { \
> + asm volatile("call __" #fn "_%P4" \
> + : "=a" (__ret_gu), "=r" (__val_gu), \
> + ASM_CALL_CONSTRAINT \
> + : "0" (ptr), "i" (sizeof(*(ptr)))); \
> + (x) = (__force __typeof__(*(ptr))) __val_gu; \
> + } \
> __builtin_expect(__ret_gu, 0); \
> })
>
> @@ -213,14 +219,18 @@ extern void __put_user_nocheck_8(void);
> int __ret_pu; \
> register __typeof__(*(ptr)) __val_pu asm("%"_ASM_AX); \
> __chk_user_ptr(ptr); \
> - __val_pu = (x); \
> - asm volatile("call __" #fn "_%P[size]" \
> - : "=c" (__ret_pu), \
> - ASM_CALL_CONSTRAINT \
> - : "0" (ptr), \
> - "r" (__val_pu), \
> - [size] "i" (sizeof(*(ptr))) \
> - :"ebx"); \
> + if (unlikely(should_fail_usercopy())) { \
> + __ret_pu = -EFAULT; \
> + } else { \
> + __val_pu = (x); \
> + asm volatile("call __" #fn "_%P[size]" \
> + : "=c" (__ret_pu), \
> + ASM_CALL_CONSTRAINT \
> + : "0" (ptr), \
> + "r" (__val_pu), \
> + [size] "i" (sizeof(*(ptr))) \
> + : "ebx"); \
> + } \
> __builtin_expect(__ret_pu, 0); \
> })
>
> diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
> index 508c81e97ab1..5617b3864586 100644
> --- a/arch/x86/lib/usercopy_64.c
> +++ b/arch/x86/lib/usercopy_64.c
> @@ -7,6 +7,7 @@
> * Copyright 2002 Andi Kleen <ak@xxxxxxx>
> */
> #include <linux/export.h>
> +#include <linux/fault-inject-usercopy.h>
> #include <linux/uaccess.h>
> #include <linux/highmem.h>
>
> @@ -50,6 +51,8 @@ EXPORT_SYMBOL(__clear_user);
>
> unsigned long clear_user(void __user *to, unsigned long n)
> {
> + if (should_fail_usercopy())
> + return n;
> if (access_ok(to, n))
> return __clear_user(to, n);
> return n;
> --
> 2.29.0.rc2.309.g374f81d7ae-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
