Re: [PATCH] net: ethernet: marvell: sky2.c: Cleaning up missing null-terminate in conjunction with strncpy

From: David Miller
Date: Mon Sep 15 2014 - 16:56:33 EST


From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Date: Mon, 15 Sep 2014 13:53:39 -0700

> On Mon, 15 Sep 2014 13:07:21 -0400 (EDT)
> David Miller <davem@xxxxxxxxxxxxx> wrote:
>
>> From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
>> Date: Sun, 14 Sep 2014 19:05:57 -0700
>>
>> > On Sun, 14 Sep 2014 19:33:43 +0200
>> > Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx> wrote:
>> >
>> >> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
>> >>
>> >> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx>
>> >> ---
>> >> drivers/net/ethernet/marvell/sky2.c | 2 +-
>> >> 1 file changed, 1 insertion(+), 1 deletion(-)
>> >>
>> >> diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
>> >> index dba48a5c..7053d38 100644
>> >> --- a/drivers/net/ethernet/marvell/sky2.c
>> >> +++ b/drivers/net/ethernet/marvell/sky2.c
>> >> @@ -4907,7 +4907,7 @@ static const char *sky2_name(u8 chipid, char *buf, int sz)
>> >> };
>> >>
>> >> if (chipid >= CHIP_ID_YUKON_XL && chipid <= CHIP_ID_YUKON_OP_2)
>> >> - strncpy(buf, name[chipid - CHIP_ID_YUKON_XL], sz);
>> >> + strlcpy(buf, name[chipid - CHIP_ID_YUKON_XL], sz);
>> >> else
>> >> snprintf(buf, sz, "(chip %#x)", chipid);
>> >> return buf;
>> >
>> > Useless and unnecessary since the list of names is right there.
>> > Why not avoid the copy all together?
>> >
>> > Subject: sky2: avoid strncpy
>> >
>> > Don't use strncpy() since security thought police think it is bad.
>> >
>> > Signed-off-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
>>
>> I think providing the buffer on the stack of the thread executing the
>> probe is superior because it will allow enabling parallel probing
>> in the future.
>>
>> I don't think you have to change that aspect to achieve your goal
>> of returning the const char * string when possible.
>
> What is benefit of s/strncpy/strlcpy/ for known safe code?
> Seems like more of the checkpatch police state.
>

Stephen, read my reply again.

I didn't say to go back to the strlcpy change.

I said to use your patch, but keep the buf[] parameter allocated on
the caller's stack.

Thanks.
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