* Thomas Gleixner <[email protected]> wrote:
> On Fri, 8 Dec 2017, Darren Hart wrote:
>
> > From: "Darren Hart (VMware)" <[email protected]>
> >
> > 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) <[email protected]>
> > Cc: Thomas Gleixner <[email protected]>
> > Cc: Ingo Molnar <[email protected]>
> > Cc: Peter Zijlstra <[email protected]>
> > Cc: Darren Hart <[email protected]>
> > ---
> > 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.....
So to explain the curious timing of the mails from Thomas and me: I told Thomas
about the breakage over IRC and he found the likely bug! ;-)
Thanks,
Ingo
