[lkml]   [2018]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY_RECEIVE support for zerocopy receive
On Tue, Apr 24, 2018 at 10:27:21PM -0700, Eric Dumazet wrote:
> When adding tcp mmap() implementation, I forgot that socket lock
> had to be taken before current->mm->mmap_sem. syzbot eventually caught
> the bug.
> Since we can not lock the socket in tcp mmap() handler we have to
> split the operation in two phases.
> 1) mmap() on a tcp socket simply reserves VMA space, and nothing else.
> This operation does not involve any TCP locking.
> 2) setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) implements
> the transfert of pages from skbs to one VMA.
> This operation only uses down_read(&current->mm->mmap_sem) after
> holding TCP lock, thus solving the lockdep issue.
> This new implementation was suggested by Andy Lutomirski with great details.

Thanks, this looks much more sensible to me.

 \ /
  Last update: 2018-04-25 08:29    [W:0.093 / U:9.808 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site