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bpf: allow b/h/w/dw access for bpf's cb in ctx

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When structs are used to store temporary state in cb[] buffer that is
used with programs and among tail calls, then the generated code will
not always access the buffer in bpf_w chunks. We can ease programming
of it and let this act more natural by allowing for aligned b/h/w/dw
sized access for cb[] ctx member. Various test cases are attached as
well for the selftest suite. Potentially, this can also be reused for
other program types to pass data around.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann
2017-01-12 11:51:33 +01:00
committed by David S. Miller
parent 6b8cc1d11e
commit 62c7989b24
3 changed files with 478 additions and 13 deletions
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41
net/core/filter.c
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@@ -2776,11 +2776,33 @@ static bool __is_valid_access(int off, int size)
{
if (off < 0 || off >= sizeof(struct __sk_buff))
return false;
/* The verifier guarantees that size > 0. */
if (off % size != 0)
return false;
if (size != sizeof(__u32))
return false;
switch (off) {
case offsetof(struct __sk_buff, cb[0]) ...
offsetof(struct __sk_buff, cb[4]) + sizeof(__u32) - 1:
if (size == sizeof(__u16) &&
off > offsetof(struct __sk_buff, cb[4]) + sizeof(__u16))
return false;
if (size == sizeof(__u32) &&
off > offsetof(struct __sk_buff, cb[4]))
return false;
if (size == sizeof(__u64) &&
off > offsetof(struct __sk_buff, cb[2]))
return false;
if (size != sizeof(__u8) &&
size != sizeof(__u16) &&
size != sizeof(__u32) &&
size != sizeof(__u64))
return false;
break;
default:
if (size != sizeof(__u32))
return false;
}
return true;
}
@@ -2799,7 +2821,7 @@ static bool sk_filter_is_valid_access(int off, int size,
if (type == BPF_WRITE) {
switch (off) {
case offsetof(struct __sk_buff, cb[0]) ...
offsetof(struct __sk_buff, cb[4]):
offsetof(struct __sk_buff, cb[4]) + sizeof(__u32) - 1:
break;
default:
return false;
@@ -2823,7 +2845,7 @@ static bool lwt_is_valid_access(int off, int size,
case offsetof(struct __sk_buff, mark):
case offsetof(struct __sk_buff, priority):
case offsetof(struct __sk_buff, cb[0]) ...
offsetof(struct __sk_buff, cb[4]):
offsetof(struct __sk_buff, cb[4]) + sizeof(__u32) - 1:
break;
default:
return false;
@@ -2915,7 +2937,7 @@ static bool tc_cls_act_is_valid_access(int off, int size,
case offsetof(struct __sk_buff, tc_index):
case offsetof(struct __sk_buff, priority):
case offsetof(struct __sk_buff, cb[0]) ...
offsetof(struct __sk_buff, cb[4]):
offsetof(struct __sk_buff, cb[4]) + sizeof(__u32) - 1:
case offsetof(struct __sk_buff, tc_classid):
break;
default:
@@ -3066,8 +3088,11 @@ static u32 sk_filter_convert_ctx_access(enum bpf_access_type type,
si->dst_reg, si->src_reg, insn);
case offsetof(struct __sk_buff, cb[0]) ...
offsetof(struct __sk_buff, cb[4]):
offsetof(struct __sk_buff, cb[4]) + sizeof(__u32) - 1:
BUILD_BUG_ON(FIELD_SIZEOF(struct qdisc_skb_cb, data) < 20);
BUILD_BUG_ON((offsetof(struct sk_buff, cb) +
offsetof(struct qdisc_skb_cb, data)) %
sizeof(__u64));
prog->cb_access = 1;
off = si->off;
@@ -3075,10 +3100,10 @@ static u32 sk_filter_convert_ctx_access(enum bpf_access_type type,
off += offsetof(struct sk_buff, cb);
off += offsetof(struct qdisc_skb_cb, data);
if (type == BPF_WRITE)
*insn++ = BPF_STX_MEM(BPF_W, si->dst_reg,
*insn++ = BPF_STX_MEM(BPF_SIZE(si->code), si->dst_reg,
si->src_reg, off);
else
*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg,
*insn++ = BPF_LDX_MEM(BPF_SIZE(si->code), si->dst_reg,
si->src_reg, off);
break;