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Message-ID: <20160506085300.GE24044@pd.tnic>
Date: Fri, 6 May 2016 10:53:01 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>
Cc: torvalds@...ux-foundation.org, hpa@...or.com, dyoung@...hat.com,
tglx@...utronix.de, keescook@...omium.org, luto@...nel.org,
peterz@...radead.org, dvlasenk@...hat.com,
linux-kernel@...r.kernel.org, brgerst@...il.com,
luto@...capital.net, akpm@...ux-foundation.org, bhe@...hat.com,
mingo@...nel.org, yinghai@...nel.org, vgoyal@...hat.com,
linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/boot] x86/boot: Clean up pointer casting
On Fri, May 06, 2016 at 12:45:41AM -0700, tip-bot for Kees Cook wrote:
> Commit-ID: 2bc1cd39fa9f659956b25e500422e700a6cd4ec3
> Gitweb: http://git.kernel.org/tip/2bc1cd39fa9f659956b25e500422e700a6cd4ec3
> Author: Kees Cook <keescook@...omium.org>
> AuthorDate: Thu, 5 May 2016 15:13:46 -0700
> Committer: Ingo Molnar <mingo@...nel.org>
> CommitDate: Fri, 6 May 2016 09:00:59 +0200
>
> x86/boot: Clean up pointer casting
...
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index f1818d9..2072d82 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -305,12 +305,21 @@ static unsigned long find_random_addr(unsigned long minimum,
> return slots_fetch_random();
> }
>
> -unsigned char *choose_random_location(unsigned char *input,
> +unsigned char *choose_random_location(unsigned char *input_ptr,
> unsigned long input_size,
> - unsigned char *output,
> + unsigned char *output_ptr,
> unsigned long output_size)
> {
> - unsigned long choice = (unsigned long)output;
> + /*
> + * The caller of choose_random_location() uses unsigned char * for
> + * buffer pointers since it performs decompression, elf parsing, etc.
> + * Since this code examines addresses much more numerically,
> + * unsigned long is used internally here. Instead of sprinkling
> + * more casts into extract_kernel, do them here and at return.
> + */
> + unsigned long input = (unsigned long)input_ptr;
> + unsigned long output = (unsigned long)output_ptr;
This can be simplified even further:
---
From: Borislav Petkov <bp@...e.de>
Date: Fri, 6 May 2016 10:43:21 +0200
Subject: [PATCH] x86/boot: Simplify pointer casting in
choose_random_location()
Pass them down as unsigned long directly and get rid of more casting and
assignments.
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Kees Cook <keescook@...omium.org>
---
arch/x86/boot/compressed/kaslr.c | 17 ++++++-----------
arch/x86/boot/compressed/misc.c | 3 ++-
arch/x86/boot/compressed/misc.h | 8 ++++----
3 files changed, 12 insertions(+), 16 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 6392f0041b8a..a49f48317dad 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -350,20 +350,15 @@ static unsigned long find_random_addr(unsigned long minimum,
return slots_fetch_random();
}
-unsigned char *choose_random_location(unsigned char *input_ptr,
+/*
+ * Since this function examines addresses much more numerically,
+ * it takes the input and output pointers as unsigned long.
+ */
+unsigned char *choose_random_location(unsigned long input,
unsigned long input_size,
- unsigned char *output_ptr,
+ unsigned long output,
unsigned long output_size)
{
- /*
- * The caller of choose_random_location() uses unsigned char * for
- * buffer pointers since it performs decompression, elf parsing, etc.
- * Since this code examines addresses much more numerically,
- * unsigned long is used internally here. Instead of sprinkling
- * more casts into extract_kernel, do them here and at return.
- */
- unsigned long input = (unsigned long)input_ptr;
- unsigned long output = (unsigned long)output_ptr;
unsigned long choice = output;
unsigned long random_addr;
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 9536d778149e..f14db4e21654 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -366,7 +366,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
* the entire decompressed kernel plus relocation table, or the
* entire decompressed kernel plus .bss and .brk sections.
*/
- output = choose_random_location(input_data, input_len, output,
+ output = choose_random_location((unsigned long)input_data, input_len,
+ (unsigned long)output,
max(output_len, kernel_total_size));
/* Validate memory location choices. */
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 1f23d022d241..1c793463328b 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -67,17 +67,17 @@ int cmdline_find_option_bool(const char *option);
#if CONFIG_RANDOMIZE_BASE
/* kaslr.c */
-unsigned char *choose_random_location(unsigned char *input_ptr,
+unsigned char *choose_random_location(unsigned long input_ptr,
unsigned long input_size,
- unsigned char *output_ptr,
+ unsigned long output_ptr,
unsigned long output_size);
/* cpuflags.c */
bool has_cpuflag(int flag);
#else
static inline
-unsigned char *choose_random_location(unsigned char *input_ptr,
+unsigned char *choose_random_location(unsigned long input_ptr,
unsigned long input_size,
- unsigned char *output_ptr,
+ unsigned long output_ptr,
unsigned long output_size)
{
return output_ptr;
--
2.7.3
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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