From: Martin KaFai Lau <ka...@fb.com>
[ Upstream commit d623876646be119439999a229a2c3ce30fd197fb ]
By adding this test to test_verifier:
{
"reference tracking: access sk->src_ip4 (narrow load)",
.insns = {
BPF_SK_LOOKUP,
BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3),
BPF_LDX_MEM(BPF_H, BPF_REG_2, BPF_REG_0, offsetof(struct bpf_sock,
src_ip4) + 2),
BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
BPF_EMIT_CALL(BPF_FUNC_sk_release),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.result = ACCEPT,
},
The above test loads 2 bytes from sk->src_ip4 where
sk is obtained by bpf_sk_lookup_tcp().
It hits an internal verifier error from convert_ctx_accesses():
[root@arch-fb-vm1 bpf]# ./test_verifier 665 665
Failed to load prog 'Invalid argument'!
0: (b7) r2 = 0
1: (63) *(u32 *)(r10 -8) = r2
2: (7b) *(u64 *)(r10 -16) = r2
3: (7b) *(u64 *)(r10 -24) = r2
4: (7b) *(u64 *)(r10 -32) = r2
5: (7b) *(u64 *)(r10 -40) = r2
6: (7b) *(u64 *)(r10 -48) = r2
7: (bf) r2 = r10
8: (07) r2 += -48
9: (b7) r3 = 36
10: (b7) r4 = 0
11: (b7) r5 = 0
12: (85) call bpf_sk_lookup_tcp#84
13: (bf) r6 = r0
14: (15) if r0 == 0x0 goto pc+3
R0=sock(id=1,off=0,imm=0) R6=sock(id=1,off=0,imm=0) R10=fp0,call_-1
fp-8=????0000 fp-16=0000mmmm fp-24=mmmmmmmm fp-32=mmmmmmmm fp-40=mmmmmmmm
fp-48=mmmmmmmm refs=1
15: (69) r2 = *(u16 *)(r0 +26)
16: (bf) r1 = r6
17: (85) call bpf_sk_release#86
18: (95) exit
from 14 to 18: safe
processed 20 insns (limit 131072), stack depth 48
bpf verifier is misconfigured
Summary: 0 PASSED, 0 SKIPPED, 1 FAILED
The bpf_sock_is_valid_access() is expecting src_ip4 can be narrowly
loaded (meaning load any 1 or 2 bytes of the src_ip4) by
marking info->ctx_field_size. However, this marked
ctx_field_size is not used. This patch fixes it.
Due to the recent refactoring in test_verifier,
this new test will be added to the bpf-next branch
(together with the bpf_tcp_sock patchset)
to avoid merge conflict.
Fixes: c64b7983288e ("bpf: Add PTR_TO_SOCKET verifier type")
Cc: Joe Stringer <j...@wand.net.nz>
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
Acked-by: Joe Stringer <j...@wand.net.nz>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
kernel/bpf/verifier.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 63a9253679f2..c0fb76d1e771 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1533,12 +1533,13 @@ static int check_flow_keys_access(struct
bpf_verifier_env *env, int off,
return 0;
}
-static int check_sock_access(struct bpf_verifier_env *env, u32 regno, int off,
- int size, enum bpf_access_type t)
+static int check_sock_access(struct bpf_verifier_env *env, int insn_idx,
+ u32 regno, int off, int size,
+ enum bpf_access_type t)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = ®s[regno];
- struct bpf_insn_access_aux info;
+ struct bpf_insn_access_aux info = {};
if (reg->smin_value < 0) {
verbose(env, "R%d min value is negative, either use unsigned
index or do a if (index >=0) check.\n",
@@ -1552,6 +1553,8 @@ static int check_sock_access(struct bpf_verifier_env
*env, u32 regno, int off,
return -EACCES;
}
+ env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
+
return 0;
}
@@ -1948,7 +1951,7 @@ static int check_mem_access(struct bpf_verifier_env *env,
int insn_idx, u32 regn
verbose(env, "cannot write into socket\n");
return -EACCES;
}
- err = check_sock_access(env, regno, off, size, t);
+ err = check_sock_access(env, insn_idx, regno, off, size, t);
if (!err && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else {
--
2.19.1
