On 10/27/2015 03:17 AM, Andy Shevchenko wrote:
> On Mon, 2015-10-26 at 14:33 -0500, Nathan Fontenot wrote:
>> Commit a030e1e4bbd085bbcfd0a23f8d355fcd41f39bed made a change to use
>> kstrndup() instead of kmalloc() + strlcpy() in
>> pseries_of_derive_parent()
>> which introduces a subtle change in the parent path name generated.
>> The kstrndup() routine will copy n characters followed by a
>> terminating null,
>> whereas strlcpy() will copy n-1 characters and add a terminating
>> null.
>
> Nice catch!
> One comment below.
>
>>
>> This slight difference results in having a parent path that includes
>> the
>> trailing '/' character, i.e. "/cpus/" vs. "/cpus". This then causes
>> the
>> subsequent call to of_find_node_by_path() to fail, and in the case of
>> DLPAR add operations, the DLPAR request fails.
>>
>> This patch reduces the total length of the string to copy in kstrndup
>> by 1
>> so we no longer copy the trailing '/'.
>>
>> Signed-off-by: Nathan Fontenot <nf...@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/platforms/pseries/of_helpers.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/of_helpers.c
>> b/arch/powerpc/platforms/pseries/of_helpers.c
>> index 4417afe..6d90378 100644
>> --- a/arch/powerpc/platforms/pseries/of_helpers.c
>> +++ b/arch/powerpc/platforms/pseries/of_helpers.c
>> @@ -24,7 +24,7 @@ struct device_node *pseries_of_derive_parent(const
>> char *path)
>> return ERR_PTR(-EINVAL);
>>
>> if (tail > path + 1) {
>> - parent_path = kstrndup(path, tail - path,
>> GFP_KERNEL);
>> + parent_path = kstrndup(path, (tail - 1) - path,
>> GFP_KERNEL);
>
> Since previous line has (tail > path + 1) which is equivalent to (tail
> - 1 > path), can we amend both?
>
> For example (might be better, but first comes to my mind)
>
> const char *tail = kbasename(path) - 1;
Agreed. I'll send out a v2 of the patch with this update and add a comment
to indicate we do not want to include the trailing '\' character.
-Nathan
>
> ...
>
> if (tail > path) {
>
>
>> if (!parent_path)
>> return ERR_PTR(-ENOMEM);
>> }
>>
>
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