Patch "bpf: fix divides by zero" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    bpf: fix divides by zero

to the 4.4-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-fix-divides-by-zero.patch
and it can be found in the queue-4.4 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 foo@baz Thu Feb  1 09:05:44 CET 2018
From: Daniel Borkmann <daniel@iogearbox.net>
Date: Tue, 30 Jan 2018 03:37:44 +0100
Subject: bpf: fix divides by zero
To: gregkh@linuxfoundation.org
Cc: ast@kernel.org, daniel@iogearbox.net, stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>
Message-ID: <cdf90cab74cbd2ef542fc5f982b55f423a52a5b5.1517279268.git.daniel@iogearbox.net>

From: Eric Dumazet <edumazet@google.com>

[ upstream commit c366287ebd698ef5e3de300d90cd62ee9ee7373e ]

Divides by zero are not nice, lets avoid them if possible.

Also do_div() seems not needed when dealing with 32bit operands,
but this seems a minor detail.

Fixes: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's instruction set")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/bpf/core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -444,7 +444,7 @@ select_insn:
 		DST = tmp;
 		CONT;
 	ALU_MOD_X:
-		if (unlikely(SRC == 0))
+		if (unlikely((u32)SRC == 0))
 			return 0;
 		tmp = (u32) DST;
 		DST = do_div(tmp, (u32) SRC);
@@ -463,7 +463,7 @@ select_insn:
 		DST = div64_u64(DST, SRC);
 		CONT;
 	ALU_DIV_X:
-		if (unlikely(SRC == 0))
+		if (unlikely((u32)SRC == 0))
 			return 0;
 		tmp = (u32) DST;
 		do_div(tmp, (u32) SRC);


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

queue-4.4/bpf-fix-branch-pruning-logic.patch
queue-4.4/bpf-avoid-false-sharing-of-map-refcount-with-max_entries.patch
queue-4.4/x86-bpf_jit-small-optimization-in-emit_bpf_tail_call.patch
queue-4.4/bpf-reject-stores-into-ctx-via-st-and-xadd.patch
queue-4.4/bpf-fix-32-bit-divide-by-zero.patch
queue-4.4/bpf-fix-bpf_tail_call-x64-jit.patch
queue-4.4/bpf-arsh-is-not-supported-in-32-bit-alu-thus-reject-it.patch
queue-4.4/bpf-fix-divides-by-zero.patch
queue-4.4/bpf-introduce-bpf_jit_always_on-config.patch