[PATCH] commands: md: don't leak heap memory with unaligned accesses

[PATCH] commands: md: don't leak heap memory with unaligned accesses

[Ahmad Fatoum]

Doing unaligned near file end returns bogus results:

	barebox@Sandbox:/ md -s /dev/stickypage 4095
	00000fff: 959ff8ff                                           .

That 0x959ff8 is heap memory next to the buffer md had allocated.
Fix this by adding some zeroed padding after the buffer, so it instead
reads:

	00000fff: 000000ff                                           .

This is arguably better user experience.
This only applies to non-mappable fd's. For e.g. /dev/mem, unaligned
accesses will still be passed as-is.

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
---
 commands/md.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/commands/md.c b/commands/md.c
index ef6a1e1bc0b1..d80c7cca0ce4 100644
--- a/commands/md.c
+++ b/commands/md.c
@@ -59,7 +59,7 @@ static int do_mem_md(int argc, char *argv[])
 		goto out;
 	}
 
-	buf = xmalloc(RW_BUF_SIZE);
+	buf = xzalloc(RW_BUF_SIZE + 7);
 
 	do {
 		now = min(size, (loff_t)RW_BUF_SIZE);
-- 
2.32.0.rc0


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Re: [PATCH] commands: md: don't leak heap memory with unaligned accesses

[Sascha Hauer]

On Sat, Jun 19, 2021 at 07:42:17AM +0200, Ahmad Fatoum wrote:
> Doing unaligned near file end returns bogus results:
> 
> 	barebox@Sandbox:/ md -s /dev/stickypage 4095
> 	00000fff: 959ff8ff                                           .
> 
> That 0x959ff8 is heap memory next to the buffer md had allocated.
> Fix this by adding some zeroed padding after the buffer, so it instead
> reads:
> 
> 	00000fff: 000000ff                                           .
> 
> This is arguably better user experience.
> This only applies to non-mappable fd's. For e.g. /dev/mem, unaligned
> accesses will still be passed as-is.
> 
> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
> ---
>  commands/md.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks

Sascha

> 
> diff --git a/commands/md.c b/commands/md.c
> index ef6a1e1bc0b1..d80c7cca0ce4 100644
> --- a/commands/md.c
> +++ b/commands/md.c
> @@ -59,7 +59,7 @@ static int do_mem_md(int argc, char *argv[])
>  		goto out;
>  	}
>  
> -	buf = xmalloc(RW_BUF_SIZE);
> +	buf = xzalloc(RW_BUF_SIZE + 7);
>  
>  	do {
>  		now = min(size, (loff_t)RW_BUF_SIZE);
> -- 
> 2.32.0.rc0
> 
> 
> _______________________________________________
> barebox mailing list
> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox
> 

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