Re: [PATCH v1 2/7] fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM

Mike Rapoport
2021-05-02T06:31:36Z

On Thu, Apr 29, 2021 at 02:25:14PM +0200, David Hildenbrand wrote:
> Let's resturcture the code, using switch-case, and checking pfn_is_ram()
> only when we are dealing with KCORE_RAM.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>

> ---
> fs/proc/kcore.c | 35 +++++++++++++++++++++++++++--------
> 1 file changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> index 09f77d3c6e15..ed6fbb3bd50c 100644
> --- a/fs/proc/kcore.c
> +++ b/fs/proc/kcore.c
> @@ -483,25 +483,36 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
> goto out;
> }
> m = NULL; /* skip the list anchor */
> - } else if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) {
> - if (clear_user(buffer, tsz)) {
> - ret = -EFAULT;
> - goto out;
> - }
> - } else if (m->type == KCORE_VMALLOC) {
> + goto skip;
> + }
> +
> + switch (m->type) {
> + case KCORE_VMALLOC:
> vread(buf, (char *)start, tsz);
> /* we have to zero-fill user buffer even if no read */
> if (copy_to_user(buffer, buf, tsz)) {
> ret = -EFAULT;
> goto out;
> }
> - } else if (m->type == KCORE_USER) {
> + break;
> + case KCORE_USER:
> /* User page is handled prior to normal kernel page: */
> if (copy_to_user(buffer, (char *)start, tsz)) {
> ret = -EFAULT;
> goto out;
> }
> - } else {
> + break;
> + case KCORE_RAM:
> + if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) {
> + if (clear_user(buffer, tsz)) {
> + ret = -EFAULT;
> + goto out;
> + }
> + break;
> + }
> + fallthrough;
> + case KCORE_VMEMMAP:
> + case KCORE_TEXT:
> if (kern_addr_valid(start)) {
> /*
> * Using bounce buffer to bypass the
> @@ -525,7 +536,15 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
> goto out;
> }
> }
> + break;
> + default:
> + pr_warn_once("Unhandled KCORE type: %d\n", m->type);
> + if (clear_user(buffer, tsz)) {
> + ret = -EFAULT;
> + goto out;
> + }
> }
> +skip:
> buflen -= tsz;
> *fpos += tsz;
> buffer += tsz;
> --
> 2.30.2
>

--
Sincerely yours,
Mike.