On Wed, 2016-05-18 at 16:14 +0300, Andrey Ryabinin wrote:
>
> On 05/18/2016 04:03 PM, Eric Dumazet wrote:
> > On Wed, 2016-05-18 at 15:03 +0300, Andrey Ryabinin wrote:
> >> ->sk_shutdown bits share one bitfield with some other bits in sock struct,
> >> such as ->sk_no_check_[r,t]x, ->sk_userlocks ...
> >> sock_setsockopt() may write to these bits, while holding the socket lock.
> >>
> >> In case of AF_UNIX sockets, we change ->sk_shutdown bits while holding only
> >> unix_state_lock(). So concurrent setsockopt() and shutdown() may lead
> >> to corrupting these bits.
> >>
> >> Fix this by moving ->sk_shutdown bits out of bitfield into a separate byte.
> >> This will not change the 'struct sock' size since ->sk_shutdown moved into
> >> previously unused 16-bit hole.
> >>
> >> Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
> >> Suggested-by: Hannes Frederic Sowa <han...@stressinduktion.org>
> >> ---
> >> include/net/sock.h | 4 ++--
> >> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/include/net/sock.h b/include/net/sock.h
> >> index c9c8b19..04dc131 100644
> >> --- a/include/net/sock.h
> >> +++ b/include/net/sock.h
> >> @@ -383,8 +383,7 @@ struct sock {
> >> int sk_sndbuf;
> >> struct sk_buff_head sk_write_queue;
> >> kmemcheck_bitfield_begin(flags);
> >> - unsigned int sk_shutdown : 2,
> >
> >
> > Please replace by a padding, so that sk_protocol is sill a byte,
> > not 8 bits spaning 2 bytes in memory.
>
> I think, it would be better to have something like this:
>
> u16 sk_type;
> u8 sk_protocol;
> kmemcheck_bitfield_begin(flags);
> u8 sk_no_check_tx : 1,
> sk_no_check_rx : 1,
> sk_userlocks : 4,
> kmemcheck_bitfield_end(flags);
>
>
No. This would add extra 32 bits for KMEMCHECK users.
Check kmemcheck_bitfield_begin definition.
These fields are together to fill 32 bits.
