futex_wait_setup() first tries to read the user value with page faults
disabled (because it holds a lock, and so cannot sleep). If that read
fails it drops the lock and tries again.
But there are now two reasons why the user space read can fail. Either:
1) legacy case of a page fault, in which case it is reasonable to retry
2) machine check on the user address, bad idea to re-read
Check for the ENXIO return code from the first get_user() call and
immediately return an error without re-reading the futex.
Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
kernel/futex.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index c47d1015d759..b11166712a9f 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -723,7 +723,7 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from)
ret = __get_user(*dest, from);
pagefault_enable();
- return ret ? -EFAULT : 0;
+ return (ret == -ENXIO) ? ret : ret ? -EFAULT : 0;
}
@@ -2658,6 +2658,9 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
if (ret) {
queue_unlock(*hb);
+ if (ret == -ENXIO)
+ return ret;
+
ret = get_user(uval, uaddr);
if (ret)
return ret;
--
2.21.1
