Patch "bpf, x64: increase number of passes" has been added to the 4.9-stable tree

Patch "bpf, x64: increase number of passes" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    bpf, x64: increase number of passes

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-x64-increase-number-of-passes.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6007b080d2e2adb7af22bf29165f0594ea12b34c Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <daniel@iogearbox.net>
Date: Wed, 7 Mar 2018 22:10:01 +0100
Subject: bpf, x64: increase number of passes

From: Daniel Borkmann <daniel@iogearbox.net>

commit 6007b080d2e2adb7af22bf29165f0594ea12b34c upstream.

In Cilium some of the main programs we run today are hitting 9 passes
on x64's JIT compiler, and we've had cases already where we surpassed
the limit where the JIT then punts the program to the interpreter
instead, leading to insertion failures due to CONFIG_BPF_JIT_ALWAYS_ON
or insertion failures due to the prog array owner being JITed but the
program to insert not (both must have the same JITed/non-JITed property).

One concrete case the program image shrunk from 12,767 bytes down to
10,288 bytes where the image converged after 16 steps. I've measured
that this took 340us in the JIT until it converges on my i7-6600U. Thus,
increase the original limit we had from day one where the JIT covered
cBPF only back then before we run into the case (as similar with the
complexity limit) where we trip over this and hit program rejections.
Also add a cond_resched() into the compilation loop, the JIT process
runs without any locks and may sleep anyway.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/net/bpf_jit_comp.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1135,7 +1135,7 @@ struct bpf_prog *bpf_int_jit_compile(str
 	 * may converge on the last pass. In such case do one more
 	 * pass to emit the final image
 	 */
-	for (pass = 0; pass < 10 || image; pass++) {
+	for (pass = 0; pass < 20 || image; pass++) {
 		proglen = do_jit(prog, addrs, image, oldproglen, &ctx);
 		if (proglen <= 0) {
 			image = NULL;
@@ -1162,6 +1162,7 @@ struct bpf_prog *bpf_int_jit_compile(str
 			}
 		}
 		oldproglen = proglen;
+		cond_resched();
 	}
 
 	if (bpf_jit_enable > 1)


Patches currently in stable-queue which might be from daniel@iogearbox.net are

queue-4.9/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch
queue-4.9/bpf-skip-unnecessary-capability-check.patch
queue-4.9/bpf-x64-increase-number-of-passes.patch