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Date:   Thu, 28 May 2020 09:49:13 -0400
From:   Qian Cai <cai@lca.pw>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Leon Romanovsky <leonro@mellanox.com>,
        Leon Romanovsky <leon@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH 2/3] kasan: move kasan_report() into report.c
Message-ID: <20200528134913.GA1810@lca.pw>
References: <29bd753d5ff5596425905b0b07f51153e2345cc1.1589297433.git.andreyknvl@google.com>
 <78a81fde6eeda9db72a7fd55fbc33173a515e4b1.1589297433.git.andreyknvl@google.com>
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On Tue, May 12, 2020 at 05:33:20PM +0200, 'Andrey Konovalov' via kasan-dev wrote:
> The kasan_report() functions belongs to report.c, as it's a common
> functions that does error reporting.
> 
> Reported-by: Leon Romanovsky <leon@kernel.org>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Today's linux-next produced this with Clang 11.

mm/kasan/report.o: warning: objtool: kasan_report()+0x8a: call to __stack_chk_fail() with UACCESS enabled

kasan_report at mm/kasan/report.c:536

> ---
>  mm/kasan/common.c | 19 -------------------
>  mm/kasan/report.c | 22 ++++++++++++++++++++--
>  2 files changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 2906358e42f0..757d4074fe28 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -33,7 +33,6 @@
>  #include <linux/types.h>
>  #include <linux/vmalloc.h>
>  #include <linux/bug.h>
> -#include <linux/uaccess.h>
>  
>  #include <asm/cacheflush.h>
>  #include <asm/tlbflush.h>
> @@ -613,24 +612,6 @@ void kasan_free_shadow(const struct vm_struct *vm)
>  }
>  #endif
>  
> -extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
> -extern bool report_enabled(void);
> -
> -bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
> -{
> -	unsigned long flags = user_access_save();
> -	bool ret = false;
> -
> -	if (likely(report_enabled())) {
> -		__kasan_report(addr, size, is_write, ip);
> -		ret = true;
> -	}
> -
> -	user_access_restore(flags);
> -
> -	return ret;
> -}
> -
>  #ifdef CONFIG_MEMORY_HOTPLUG
>  static bool shadow_mapped(unsigned long addr)
>  {
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 80f23c9da6b0..51ec45407a0b 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -29,6 +29,7 @@
>  #include <linux/kasan.h>
>  #include <linux/module.h>
>  #include <linux/sched/task_stack.h>
> +#include <linux/uaccess.h>
>  
>  #include <asm/sections.h>
>  
> @@ -454,7 +455,7 @@ static void print_shadow_for_address(const void *addr)
>  	}
>  }
>  
> -bool report_enabled(void)
> +static bool report_enabled(void)
>  {
>  	if (current->kasan_depth)
>  		return false;
> @@ -479,7 +480,8 @@ 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)
> +static void __kasan_report(unsigned long addr, size_t size, bool is_write,
> +				unsigned long ip)
>  {
>  	struct kasan_access_info info;
>  	void *tagged_addr;
> @@ -518,6 +520,22 @@ void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned lon
>  	end_report(&flags);
>  }
>  
> +bool kasan_report(unsigned long addr, size_t size, bool is_write,
> +			unsigned long ip)
> +{
> +	unsigned long flags = user_access_save();
> +	bool ret = false;
> +
> +	if (likely(report_enabled())) {
> +		__kasan_report(addr, size, is_write, ip);
> +		ret = true;
> +	}
> +
> +	user_access_restore(flags);
> +
> +	return ret;
> +}
> +
>  #ifdef CONFIG_KASAN_INLINE
>  /*
>   * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
> -- 
> 2.26.2.645.ge9eca65c58-goog
> 
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