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Date: Fri, 6 Dec 2019 12:08:36 +0100 From: Guillaume Nault <gnault@...hat.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: David Miller <davem@...emloft.net>, Jakub Kicinski <jakub.kicinski@...ronome.com>, netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com> Subject: Re: [PATCH net v3 3/3] tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() On Thu, Dec 05, 2019 at 07:50:39PM -0800, Eric Dumazet wrote: > > > On 12/5/19 5:50 PM, Guillaume Nault wrote: > > Syncookies borrow the ->rx_opt.ts_recent_stamp field to store the > > timestamp of the last synflood. Protect them with READ_ONCE() and > > WRITE_ONCE() since reads and writes aren't serialised. > > > > Fixes: 264ea103a747 ("tcp: syncookies: extend validity range") > > Signed-off-by: Guillaume Nault <gnault@...hat.com> > > Signed-off-by: Eric Dumazet <edumazet@...gle.com> > > To be fair, bug was there before the patch mentioned in the Fixes: tag, > but we probably do not care enough to backport this to very old kernels. > I used this commit because it introduced the conditional in tcp_synq_overflow(), which I believe made the lockless accesses more dangerous than they were. But yes, the problem has been there forever. I have to post a v4 anyway, so I'll change this tag to reference the first commit in the tree.
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