(drop peterz from CC).

On Fri, Sep 16, 2016 at 12:22:23PM +0100, Colin King wrote:
> From: Colin Ian King <colin.k...@canonical.com>
> 
> Integer index i needs to be a signed int rather than unsigned to avoid
> a wrap-around when decrementing in the while loop.  For example, if the

Damn corner cases :-\

> debugfs_create_file fails when i is zero, the current situation will
> predecrement i in the while loop, wrapping i to the maximum signed
> integer and cause multiple out of bounds reads on dfs_fls[i].d as
> the loop interates to zero.
> 
> Also add (int) cast to fix warning that the original fix attempted
> to fix.

Thanks, that's a good catch!

But, can we keep the unsigned-ness of i as it is an index and do this
instead?

(Oh, and make it return ENODEV - that ENOMEM is just plain wrong most of
the time).

---
diff --git a/arch/x86/ras/mce_amd_inj.c b/arch/x86/ras/mce_amd_inj.c
index cd318d93099e..a2dafca467e6 100644
--- a/arch/x86/ras/mce_amd_inj.c
+++ b/arch/x86/ras/mce_amd_inj.c
@@ -457,8 +457,12 @@ static int __init init_mce_inject(void)
                                                    &i_mce,
                                                    dfs_fls[i].fops);
 
-               if (!dfs_fls[i].d)
+               if (!dfs_fls[i].d) {
+                       if (!i)
+                               return -ENODEV;
+
                        goto err_dfs_add;
+               }
        }
 
        return 0;
@@ -470,7 +474,7 @@ err_dfs_add:
        debugfs_remove(dfs_inj);
        dfs_inj = NULL;
 
-       return -ENOMEM;
+       return -ENODEV;
 }
 
 static void __exit exit_mce_inject(void)

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imend├Ârffer, Jane Smithard, Graham Norton, HRB 21284 
(AG N├╝rnberg)
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