On Mon, Dec 2, 2019 at 1:17 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > > On Mon, Dec 02, 2019 at 09:30:06AM +0100, Peter Zijlstra wrote: > > On Sun, Dec 01, 2019 at 06:49:32PM -0800, Eric Dumazet wrote: > > > > > Thanks for the link ! > > > > > > Having RO protection as a debug feature would be useful. > > > > > > I believe we have CONFIG_STRICT_MODULE_RWX (and CONFIG_STRICT_KERNEL_RWX) for that already. > > > > > > Or are we saying we also want to get rid of them ? > > > > No, in fact I'm working on making that stronger. We currently still have > > a few cases that violate the W^X rule. > > > > The thing is, when the BPF stuff is JIT'ed, the actual BPF instruction > > page is not actually executed at all, so making it RO serves no purpose, > > other than to fragment the direct map. > > Yes exactly, in that case it is only used for dumping the BPF insns back > to user space and therefore no need at all to set it RO. (The JITed image > however *is* set as RO. - Perhaps there was some confusion given your > earlier question.) May be we should also flip the default to net.core.bpf_jit_enable=1 for x86-64 ? and may be arm64 ? These two JITs are well tested and maintained.
