On Fri, 8 Dec 2017, Darren Hart wrote:
> From: "Darren Hart (VMware)" <dvh...@infradead.org>
>
> uaddr alignment is currently tested by get_futex_key(). We can catch
> misalignment earlier in sys_futex and return -EINVAL sooner. This
> simplifies get_futex_key() a little, but more importantly exits the
> kernel as soon as an invalid parameter is detected.
>
> Passes all selftests/futex testcases on a dual socket Xeon E5-2670, 16
> physical cores total, 32 threads total.
>
> Signed-off-by: Darren Hart (VMware) <dvh...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Darren Hart <dvh...@infradead.org>
> ---
> kernel/futex.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index 76ed592..c3ee6c4 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -509,8 +509,6 @@ get_futex_key(u32 __user *uaddr, int fshared, union
> futex_key *key, int rw)
> * The futex address must be "naturally" aligned.
> */
> key->both.offset = address % PAGE_SIZE;
> - if (unlikely((address % sizeof(u32)) != 0))
> - return -EINVAL;
> address -= key->both.offset;
>
> if (unlikely(!access_ok(rw, uaddr, sizeof(u32))))
> @@ -3525,6 +3523,11 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op,
> u32, val,
> u32 val2 = 0;
> int cmd = op & FUTEX_CMD_MASK;
>
> + /* Only allow for aligned uaddr variables */
> + if (unlikely((unsigned long)uaddr % sizeof(u32) != 0 ||
> + (unsigned long)uaddr2 % sizeof(u32) != 0))
Errm. How is that supposed to work? uaddr2 is not used by all opcodes.....
Thanks,
tglx
