Re: [PATCH] staging: android: Replace strcpy with strlcpy
From: SIMRAN SINGHAL
Date: Mon Mar 13 2017 - 09:14:45 EST
On Mon, Mar 13, 2017 at 6:27 PM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> On Mon, Mar 13, 2017 at 06:17:22PM +0530, SIMRAN SINGHAL wrote:
>> On Mon, Mar 13, 2017 at 6:11 PM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>> > On Sun, Mar 12, 2017 at 02:10:01AM +0530, simran singhal wrote:
>> >> Replace strcpy with strlcpy as strcpy does not check for buffer
>> >> overflow.
>> >> This is found using Flawfinder.
>> >> Signed-off-by: simran singhal <singhalsimran0@xxxxxxxxx>
>> >> ---
>> >> drivers/staging/android/ashmem.c | 3 ++-
>> >> 1 file changed, 2 insertions(+), 1 deletion(-)
>> >> diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
>> >> index 7cbad0d..eb2f4ef 100644
>> >> --- a/drivers/staging/android/ashmem.c
>> >> +++ b/drivers/staging/android/ashmem.c
>> >> @@ -548,7 +548,8 @@ static int set_name(struct ashmem_area *asma, void __user *name)
>> >> if (unlikely(asma->file))
>> >> ret = -EINVAL;
>> >> else
>> >> - strcpy(asma->name + ASHMEM_NAME_PREFIX_LEN, local_name);
>> >> + strlcpy(asma->name + ASHMEM_NAME_PREFIX_LEN, local_name,
>> >> + sizeof(asma->name + ASHMEM_NAME_PREFIX_LEN));
>> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> > This isn't right.
>> > Also please do some analysis to see if it's a real bug or a false
>> > positive. It is a false positive in this case.
>> I have already sent v3 of this in which I have used:
>> sizeof(asma->name) - ASHMEM_NAME_PREFIX_LEN
> Yeah. I saw that. It's fine, I suppose but you should have done more
> analysis to see if it was a real bug like Al and Greg suggested. The
> changelog should say something like:
> "The destination buffer is 12345 bytes long but we're copying a 10000
> character string so it can overflow." Occasionally, I will fudge a
> little bit on these changelogs to say that I have looked every where to
> determine the size of the source buffer and can't figure it out so this
> change makes it easier to audit. But I try to figure it out generally.
> Really tools should be able to show that this code is safe. They
> currently don't so far as I know, but they should. It's a matter of
> waiting a year for Smatch to improve.
Will keep this in mind.
> dan carpenter