Re: [PATCH v7 18/43] instrumented.h: add KMSAN support

[youling 257]

I test this patch fix my problem.

2022-10-22 4:37 GMT+08:00, Alexander Potapenko <glider@xxxxxxxxxx>:
> On Fri, Oct 21, 2022 at 8:19 AM youling 257 <youling257@xxxxxxxxx> wrote:
>
>> CONFIG_DEBUG_INFO=y
>> CONFIG_AS_HAS_NON_CONST_LEB128=y
>> # CONFIG_DEBUG_INFO_NONE is not set
>> CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
>> # CONFIG_DEBUG_INFO_DWARF4 is not set
>> # CONFIG_DEBUG_INFO_DWARF5 is not set
>> # CONFIG_DEBUG_INFO_REDUCED is not set
>> # CONFIG_DEBUG_INFO_COMPRESSED is not set
>> # CONFIG_DEBUG_INFO_SPLIT is not set
>> # CONFIG_DEBUG_INFO_BTF is not set
>> # CONFIG_GDB_SCRIPTS is not set
>>
>> perf top still no function name.
>>
>> 12.90%  [kernel]              [k] 0xffffffff833dfa64
>>
>
> I think I know what's going on. The two functions that differ with and
> without the patch were passing an incremented pointer to unsafe_put_user(),
> which is a macro, e.g.:
>
>    unsafe_put_user((compat_ulong_t)m, umask++, Efault);
>
> Because that macro didn't evaluate its second parameter, "umask++" was
> passed to a call to kmsan_copy_to_user(), which resulted in an extra
> increment of umask.
> This probably violated some expectations of the userspace app, which in
> turn led to repetitive kernel calls.
>
> Could you please check if the patch below fixes the problem for you?
>
> diff --git a/arch/x86/include/asm/uaccess.h
> b/arch/x86/include/asm/uaccess.h
> index 8bc614cfe21b9..1cc756eafa447 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -254,24 +254,25 @@ extern void __put_user_nocheck_8(void);
>  #define __put_user_size(x, ptr, size, label)                           \
>  do {                                                                   \
>         __typeof__(*(ptr)) __x = (x); /* eval x once */                 \
> -       __chk_user_ptr(ptr);                                            \
> +       __typeof__(ptr) __ptr = (ptr); /* eval ptr once */              \
> +       __chk_user_ptr(__ptr);                                          \
>         switch (size) {                                                 \
>         case 1:                                                         \
> -               __put_user_goto(__x, ptr, "b", "iq", label);            \
> +               __put_user_goto(__x, __ptr, "b", "iq", label);          \
>                 break;                                                  \
>         case 2:                                                         \
> -               __put_user_goto(__x, ptr, "w", "ir", label);            \
> +               __put_user_goto(__x, __ptr, "w", "ir", label);          \
>                 break;                                                  \
>         case 4:                                                         \
> -               __put_user_goto(__x, ptr, "l", "ir", label);            \
> +               __put_user_goto(__x, __ptr, "l", "ir", label);          \
>                 break;                                                  \
>         case 8:                                                         \
> -               __put_user_goto_u64(__x, ptr, label);                   \
> +               __put_user_goto_u64(__x, __ptr, label);                 \
>                 break;                                                  \
>         default:                                                        \
>                 __put_user_bad();                                       \
>         }                                                               \
> -       instrument_put_user(__x, ptr, size);                            \
> +       instrument_put_user(__x, __ptr, size);                          \
>  } while (0)
>
>  #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
>