This is a note to let you know that I've just added the patch titled
bpf: arsh is not supported in 32 bit alu thus reject it
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-arsh-is-not-supported-in-32-bit-alu-thus-reject-it.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@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Feb 1 09:05:44 CET 2018
From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Date: Tue, 30 Jan 2018 03:37:42 +0100
Subject: bpf: arsh is not supported in 32 bit alu thus reject it
To: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: ast@xxxxxxxxxx, daniel@xxxxxxxxxxxxx, stable@xxxxxxxxxxxxxxx
Message-ID: <60932351924d42bf28628b0a01a693602cc0d9b9.1517279268.git.daniel@xxxxxxxxxxxxx>
From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
[ upstream commit 7891a87efc7116590eaba57acc3c422487802c6f ]
The following snippet was throwing an 'unknown opcode cc' warning
in BPF interpreter:
0: (18) r0 = 0x0
2: (7b) *(u64 *)(r10 -16) = r0
3: (cc) (u32) r0 s>>= (u32) r0
4: (95) exit
Although a number of JITs do support BPF_ALU | BPF_ARSH | BPF_{K,X}
generation, not all of them do and interpreter does neither. We can
leave existing ones and implement it later in bpf-next for the
remaining ones, but reject this properly in verifier for the time
being.
Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)")
Reported-by: syzbot+93c4904c5c70348a6890@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/verifier.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1165,6 +1165,11 @@ static int check_alu_op(struct verifier_
return -EINVAL;
}
+ if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) {
+ verbose("BPF_ARSH not supported for 32 bit ALU\n");
+ return -EINVAL;
+ }
+
if ((opcode == BPF_LSH || opcode == BPF_RSH ||
opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
Patches currently in stable-queue which might be from daniel@xxxxxxxxxxxxx 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