diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch new file mode 100644 index 00000000..fc0cb2fc --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch @@ -0,0 +1,83 @@ +From c7d695dd43368b0231ed509066131696d1533738 Mon Sep 17 00:00:00 2001 +From: Daniel Borkmann <daniel@iogearbox.net> +Date: Thu, 29 Jun 2017 03:04:59 +0200 +Subject: [PATCH 095/103] bpf: prevent leaking pointer via xadd on + unpriviledged + +commit 6bdf6abc56b53103324dfd270a86580306e1a232 upstream. + +Leaking kernel addresses on unpriviledged is generally disallowed, +for example, verifier rejects the following: + + 0: (b7) r0 = 0 + 1: (18) r2 = 0xffff897e82304400 + 3: (7b) *(u64 *)(r1 +48) = r2 + R2 leaks addr into ctx + +Doing pointer arithmetic on them is also forbidden, so that they +don't turn into unknown value and then get leaked out. However, +there's xadd as a special case, where we don't check the src reg +for being a pointer register, e.g. the following will pass: + + 0: (b7) r0 = 0 + 1: (7b) *(u64 *)(r1 +48) = r0 + 2: (18) r2 = 0xffff897e82304400 ; map + 4: (db) lock *(u64 *)(r1 +48) += r2 + 5: (95) exit + +We could store the pointer into skb->cb, loose the type context, +and then read it out from there again to leak it eventually out +of a map value. Or more easily in a different variant, too: + + 0: (bf) r6 = r1 + 1: (7a) *(u64 *)(r10 -8) = 0 + 2: (bf) r2 = r10 + 3: (07) r2 += -8 + 4: (18) r1 = 0x0 + 6: (85) call bpf_map_lookup_elem#1 + 7: (15) if r0 == 0x0 goto pc+3 + R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R6=ctx R10=fp + 8: (b7) r3 = 0 + 9: (7b) *(u64 *)(r0 +0) = r3 + 10: (db) lock *(u64 *)(r0 +0) += r6 + 11: (b7) r0 = 0 + 12: (95) exit + + from 7 to 11: R0=inv,min_value=0,max_value=0 R6=ctx R10=fp + 11: (b7) r0 = 0 + 12: (95) exit + +Prevent this by checking xadd src reg for pointer types. Also +add a couple of test cases related to this. + +Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs") +Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)") +Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> +Acked-by: Alexei Starovoitov <ast@kernel.org> +Acked-by: Martin KaFai Lau <kafai@fb.com> +Acked-by: Edward Cree <ecree@solarflare.com> +Signed-off-by: David S. Miller <davem@davemloft.net> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + kernel/bpf/verifier.c | 5 +++++ + 1 file changed, 5 insertions(+) + +diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c +index bfafb53..6767670 100644 +--- a/kernel/bpf/verifier.c ++++ b/kernel/bpf/verifier.c +@@ -880,6 +880,11 @@ static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn) + if (err) + return err; + ++ if (is_pointer_value(env, insn->src_reg)) { ++ verbose("R%d leaks addr into mem\n", insn->src_reg); ++ return -EACCES; ++ } ++ + /* check whether atomic_add can read the memory */ + err = check_mem_access(env, insn->dst_reg, insn->off, + BPF_SIZE(insn->code), BPF_READ, -1); +-- +2.7.4 + |