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SubjectRe: [PATCH 2/3] devmem: handle partial kmem write/read
On Tue, Sep 15, 2009 at 05:01:30PM +0800, Wu Fengguang wrote:
> On Tue, Sep 15, 2009 at 10:38:11AM +0800, KAMEZAWA Hiroyuki wrote:
> > On Tue, 15 Sep 2009 10:18:53 +0800
> > Wu Fengguang <fengguang.wu@intel.com> wrote:
> >
> > > Return early on partial read/write, which may happen in future.
> > > (eg. hit hwpoison pages)
> > >
> > Hmm, please modify vread() as you did in vwrite() and
> >
> > ==
> > kbuf = (char *)__get_free_page(GFP_KERNEL);
> > if (!kbuf)
> > return -ENOMEM;
> > ==
> > Add __GFP_ZERO to kbuf allocation, and just ignore vread()'s return value.
> > Then, this will be much simpler.
>
> Thanks, here is the updated patch, which
> - updates vread/vwrite prototype to return 0 (or error code in future).
> - do zero fill in the callers
> Comment updates are ignored for now.

This patch also makes it trivial to add your
is_vmalloc_or_module_addr() fixes, like this :)

---
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
drivers/char/mem.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- linux-mm.orig/drivers/char/mem.c 2009-09-15 16:58:06.000000000 +0800
+++ linux-mm/drivers/char/mem.c 2009-09-15 16:58:12.000000000 +0800
@@ -446,6 +446,10 @@ static ssize_t read_kmem(struct file *fi
return -ENOMEM;
while (count > 0) {
sz = size_inside_page(p, count);
+ if (!is_vmalloc_or_module_addr((void*)p)) {
+ ret = -EFAULT;
+ break;
+ }
ret = vread(kbuf, (char *)p, sz);
if (ret)
break;
@@ -546,6 +550,10 @@ static ssize_t write_kmem(struct file *
unsigned long sz = size_inside_page(p, count);
unsigned long n;

+ if (!is_vmalloc_or_module_addr((void*)p)) {
+ ret = -EFAULT;
+ break;
+ }
n = copy_from_user(kbuf, buf, sz);
if (n) {
if (wrote + virtr)

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