[PATCH] arch: mips: sibyte: Return -EFAULT if copy_to_user() fails

[PATCH] arch: mips: sibyte: Return -EFAULT if copy_to_user() fails

[Wang Qing]

The copy_to_user() function returns the number of bytes remaining to be
copied, but we want to return -EFAULT if the copy doesn't complete.

Signed-off-by: Wang Qing <wangqing@vivo.com>
---
 arch/mips/sibyte/common/sb_tbprof.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/sibyte/common/sb_tbprof.c b/arch/mips/sibyte/common/sb_tbprof.c
index f80d7a7..eac125f
--- a/arch/mips/sibyte/common/sb_tbprof.c
+++ b/arch/mips/sibyte/common/sb_tbprof.c
@@ -465,7 +465,7 @@ static ssize_t sbprof_tb_read(struct file *filp, char *buf,
 		if (err) {
 			*offp = cur_off + cur_count - err;
 			mutex_unlock(&sbp.lock);
-			return err;
+			return -EFAULT;
 		}
 		pr_debug(DEVNAME ": read from sample %d, %d bytes\n",
 			 cur_sample, cur_count);
-- 
2.7.4

Re: [PATCH] arch: mips: sibyte: Return -EFAULT if copy_to_user() fails

[Sergei Shtylyov]

Hello!

On 01.03.2021 9:33, Wang Qing wrote:

> The copy_to_user() function returns the number of bytes remaining to be
> copied, but we want to return -EFAULT if the copy doesn't complete.

    Then 'err' is hardly a good name for that variable. :-)

> 
> Signed-off-by: Wang Qing <wangqing@vivo.com>
> ---
>   arch/mips/sibyte/common/sb_tbprof.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/mips/sibyte/common/sb_tbprof.c b/arch/mips/sibyte/common/sb_tbprof.c
> index f80d7a7..eac125f
> --- a/arch/mips/sibyte/common/sb_tbprof.c
> +++ b/arch/mips/sibyte/common/sb_tbprof.c
> @@ -465,7 +465,7 @@ static ssize_t sbprof_tb_read(struct file *filp, char *buf,
>   		if (err) {
>   			*offp = cur_off + cur_count - err;
>   			mutex_unlock(&sbp.lock);
> -			return err;
> +			return -EFAULT;
>   		}
>   		pr_debug(DEVNAME ": read from sample %d, %d bytes\n",
>   			 cur_sample, cur_count);

MBR, Sergei

Re: [PATCH] arch: mips: sibyte: Return -EFAULT if copy_to_user() fails

[Maciej W. Rozycki]

On Mon, 1 Mar 2021, Sergei Shtylyov wrote:

> > The copy_to_user() function returns the number of bytes remaining to be
> > copied, but we want to return -EFAULT if the copy doesn't complete.
> 
>    Then 'err' is hardly a good name for that variable. :-)

 Something like `left' might be better, especially as it's the sole use.  
Also it's been like this from the beginning, so:

Fixes: bb9b813bb665 ("[MIPS] Sibyte: Fix ZBbus profiler")

or maybe:

Fixes: d619f38fdacb ("[MIPS] Add bcm1480 ZBus trace support, fix wait related bugs")

(since the file was renamed from a different name with the latter commit) 
would I think be helpful for backports too.  It looks like potentially 
quite a nasty bug to me if someone actually uses this piece (I haven't).

  Maciej