On Mon, May 12, 2025 at 03:51:30PM +0100, David Howells wrote: > I'm looking at how to make sendmsg() handle page pinning - and also working > towards supporting the page refcount eventually being removed and only being > available with certain memory types. > > One of the outstanding issues is in sendmsg(). Analogously with DIO writes, > sendmsg() should be pinning memory (FOLL_PIN/GUP) rather than simply getting > refs on it before it attaches it to an sk_buff. Without this, if memory is > spliced into an AF_UNIX socket and then the process forks, that memory gets > attached to the child process, and the child can alter the data, probably by > accident, if the memory is on the stack or in the heap. > > Further, kernel services can use MSG_SPLICE_PAGES to attach memory directly to > an AF_UNIX pipe (though I'm not sure if anyone actually does this). I would possible be interested in using this for the coredump af_unix socket.
