[PATCH] EDAC, mc: Fix edac_mc_find() in case no device is found

[PATCH] EDAC, mc: Fix edac_mc_find() in case no device is found

[Robert Richter]

The function should return NULL in case no device is found, but it
always returns the last checked mc device from the list even if the
index did not match. This patch fixes this.

I did some analysis why this did not raise any issues for about 3
years and the reason is that edac_mc_find() is mostly used to search
for existing devices. Thus, the bug is not triggered.

Fixes: c73e8833bec5 ("EDAC, mc: Fix locking around mc_devices list")
Signed-off-by: Robert Richter <rrichter@marvell.com>
---
 drivers/edac/edac_mc.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 13594ffadcb3..aeeaaf30b38a 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -688,10 +688,9 @@ struct mem_ctl_info *edac_mc_find(int idx)
 		mci = list_entry(item, struct mem_ctl_info, link);
 
 		if (mci->mc_idx >= idx) {
-			if (mci->mc_idx == idx) {
-				goto unlock;
-			}
-			break;
+			if (mci->mc_idx != idx)
+				mci = NULL;
+			goto unlock;
 		}
 	}
 
-- 
2.20.1

Re: [PATCH] EDAC, mc: Fix edac_mc_find() in case no device is found

[Borislav Petkov]

On Tue, May 14, 2019 at 07:25:58AM +0000, Robert Richter wrote:
> The function should return NULL in case no device is found, but it
> always returns the last checked mc device from the list even if the
> index did not match. This patch fixes this.
> 
> I did some analysis why this did not raise any issues for about 3
> years and the reason is that edac_mc_find() is mostly used to search
> for existing devices. Thus, the bug is not triggered.
> 
> Fixes: c73e8833bec5 ("EDAC, mc: Fix locking around mc_devices list")
> Signed-off-by: Robert Richter <rrichter@marvell.com>
> ---
>  drivers/edac/edac_mc.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> index 13594ffadcb3..aeeaaf30b38a 100644
> --- a/drivers/edac/edac_mc.c
> +++ b/drivers/edac/edac_mc.c
> @@ -688,10 +688,9 @@ struct mem_ctl_info *edac_mc_find(int idx)
>  		mci = list_entry(item, struct mem_ctl_info, link);
>  
>  		if (mci->mc_idx >= idx) {
> -			if (mci->mc_idx == idx) {
> -				goto unlock;
> -			}
> -			break;
> +			if (mci->mc_idx != idx)
> +				mci = NULL;
> +			goto unlock;
>  		}
>  	}

Can we simplify this silly code even more pls? I'm pasting the whole
function instead of a diff for clarity:

---
struct mem_ctl_info *edac_mc_find(int idx)
{
        struct mem_ctl_info *mci = NULL;
        struct list_head *item;

        mutex_lock(&mem_ctls_mutex);

        list_for_each(item, &mc_devices) {
                mci = list_entry(item, struct mem_ctl_info, link);
                if (mci->mc_idx == idx)
                        goto unlock;
        }

        mci = NULL;

unlock:
        mutex_unlock(&mem_ctls_mutex);
        return mci;
---

Thx.

-- 
Regards/Gruss,
    Boris.

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