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SubjectRe: [PATCH] adjust /dev/{kmem,mem,port} write handlers
"Jan Beulich" <JBeulich@novell.com> wrote:
>
> The /dev/mem and /dev/kmem write handlers weren't fully POSIX compliant in
> that they wouldn't always force the file pointer to be updated when returning
> success status.
> The /dev/port write handler was inconsistent with the /dev/mem and /dev/kmem
> handlers in that when encountering a -EFAULT condition after already having
> written a number of items it would return -EFAULT rather than the number of
> bytes written.
>
> ...
>
> @@ -514,11 +510,10 @@ static ssize_t write_kmem(struct file *
> if (len) {
> written = copy_from_user(kbuf, buf, len);
> if (written) {
> - ssize_t ret;
> -
> + if (wrote + virtr)
> + break;
> free_page((unsigned long)kbuf);
> - ret = wrote + virtr + (len - written);
> - return ret ? ret : -EFAULT;
> + return -EFAULT;
> }
> }
> len = vwrite(kbuf, (char *)p, len);


I think write_kmem() still isn't quie right - it needs to update `p' (and
hence *ppos) to account for a partial copy_from_user(). (Please double-check)


--- devel/drivers/char/mem.c~adjust-dev-kmemmemport-write-handlers-fix 2006-03-04 22:10:55.000000000 -0800
+++ devel-akpm/drivers/char/mem.c 2006-03-04 22:15:19.000000000 -0800
@@ -504,8 +504,11 @@ static ssize_t write_kmem(struct file *
if (len) {
written = copy_from_user(kbuf, buf, len);
if (written) {
- if (wrote + virtr)
+ if (wrote + virtr) {
+ p += len - written;
+ virtr += len - written;
break;
+ }
free_page((unsigned long)kbuf);
return -EFAULT;
}
_
-
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