On Tue, Oct 19, 2021 at 10:29:51AM -0700, Yang Shi wrote:

On Mon, Oct 18, 2021 at 10:52 PM Naoya Horiguchi
[off-list ref] wrote:

quoted

On Thu, Oct 14, 2021 at 12:16:14PM -0700, Yang Shi wrote:

...

quoted

quoted

@@ -2466,7 +2467,15 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
                      return -EPERM;
      }

-     return shmem_getpage(inode, index, pagep, SGP_WRITE);
+     ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
+
+     if (*pagep && PageHWPoison(*pagep)) {

shmem_getpage() could return with pagep == NULL, so you need check ret first
to avoid NULL pointer dereference.

Realy? IIUC pagep can't be NULL. It is a pointer's pointer passed in
by the caller, for example, generic_perform_write(). Of course,
"*pagep" could be NULL.

Oh, I simply missed this. You're right. Please ignore my comment on this.

- Naoya Horiguchi