On Fri, Oct 18, 2019 at 08:33:11AM -0700, Randy Dunlap wrote:
> On 10/18/19 12:03 AM, Stephen Rothwell wrote:
> > Hi all,
> >
> > Changes since 20191017:
> >
>
> on x86_64:
> lib/usercopy.o: warning: objtool: check_zeroed_user()+0x35f: call to __ubsan_handle_shift_out_of_bounds() with UACCESS enabled
Blergh... I suppose the below will fix that. I'm a bit conflicted on it
though, the alternative is annotating more ubsan crud.
---
lib/usercopy.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/lib/usercopy.c b/lib/usercopy.c
index cbb4d9ec00f2..9c5245778dfd 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -49,21 +49,28 @@ EXPORT_SYMBOL(_copy_to_user);
*/
int check_zeroed_user(const void __user *from, size_t size)
{
+ unsigned long head_mask, tail_mask;
unsigned long val;
- uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
+ uintptr_t align;
if (unlikely(size == 0))
return 1;
- from -= align;
- size += align;
+ align = (uintptr_t) from % sizeof(unsigned long);
+ if (align) {
+ from -= align;
+ size += align;
+ head_mask = ~aligned_byte_mask(align);
+ }
+
+ tail_mask = aligned_byte_mask(size % sizeof(unsigned long));
if (!user_access_begin(from, size))
return -EFAULT;
unsafe_get_user(val, (unsigned long __user *) from, err_fault);
if (align)
- val &= ~aligned_byte_mask(align);
+ val &= head_mask;
while (size > sizeof(unsigned long)) {
if (unlikely(val))
@@ -76,7 +83,7 @@ int check_zeroed_user(const void __user *from, size_t size)
}
if (size < sizeof(unsigned long))
- val &= aligned_byte_mask(size);
+ val &= tail_mask;
done:
user_access_end();
