Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3] net: sock: move ->sk_shutdown out of bitfields. | From | Eric Dumazet <> | Date | Wed, 18 May 2016 08:31:11 -0700 |
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On Wed, 2016-05-18 at 17:36 +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 <aryabinin@virtuozzo.com> > Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org> > --- > > Changes since v1: > - move sk_shutdown into a separate byte instead of locking > AF_UNIX sockets. > > Changes since v2: > - reorder bitfields, so that sk_type/sk_protocol still fit in > separate 2-bytes/byte. >
I suggested to use an explicit padding, to clearly show that two bits are available there. You also could add a comment to remind the rules.
Something like :
diff --git a/include/net/sock.h b/include/net/sock.h index c9c8b19df27c558354687119db60c0716909ea3f..4e239a7ef4f67b1988fe119d81566d1465a2b596 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -382,8 +382,10 @@ struct sock { atomic_t sk_omem_alloc; int sk_sndbuf; struct sk_buff_head sk_write_queue; + + /* because of non atomicity rules, all changes are protected by socket lock */ kmemcheck_bitfield_begin(flags); - unsigned int sk_shutdown : 2, + unsigned int sk_padding : 2, sk_no_check_tx : 1, sk_no_check_rx : 1, sk_userlocks : 4, @@ -391,6 +393,7 @@ struct sock { sk_type : 16; #define SK_PROTOCOL_MAX U8_MAX kmemcheck_bitfield_end(flags); + int sk_wmem_queued; gfp_t sk_allocation; u32 sk_pacing_rate; /* bytes per second */ @@ -418,6 +421,7 @@ struct sock { struct timer_list sk_timer; ktime_t sk_stamp; u16 sk_tsflags; + u8 sk_shutdown; u32 sk_tskey; struct socket *sk_socket; void *sk_user_data;
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