Re: [PATCH] staging: android: Replace strcpy with strlcpy

From: Al Viro
Date: Sat Mar 11 2017 - 20:00:23 EST


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));

Trivial C quiz: given

struct ashmem_area {
char name[ASHMEM_FULL_NAME_LEN];
struct list_head unpinned_list;
struct file *file;
size_t size;
unsigned long prot_mask;
};
static int set_name(struct ashmem_area *asma, void __user *name)

what, in your opinion, would be
1) type of asma->name
2) type of asma->name + ASHMEM_NAME_PREFIX_LEN
3) value of sizeof(asma->name + ASHMEM_NAME_PREFIX_LEN)
As a bonus question,
4) what is the value of this kind of patches?

<rot13 answers>
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2) cbvagre gb pune
3) fvmr bs n cbvagre
4) fbpvbybtvpny - ernql-znqr vyyhfgengvbaf bs crevyf bs
pnetb phyg.