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Message-Id: <20190628231049.22149-1-sdf@google.com>
Date: Fri, 28 Jun 2019 16:10:48 -0700
From: Stanislav Fomichev <sdf@...gle.com>
To: netdev@...r.kernel.org, bpf@...r.kernel.org
Cc: davem@...emloft.net, ast@...nel.org, daniel@...earbox.net,
Stanislav Fomichev <sdf@...gle.com>,
Andrii Nakryiko <andriin@...com>, Yonghong Song <yhs@...com>,
kernel test robot <rong.a.chen@...el.com>
Subject: [PATCH bpf-next 1/2] bpf: allow wide (u64) aligned stores for some
fields of bpf_sock_addr
Since commit cd17d7770578 ("bpf/tools: sync bpf.h") clang decided
that it can do a single u64 store into user_ip6[2] instead of two
separate u32 ones:
# 17: (18) r2 = 0x100000000000000
# ; ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2);
# 19: (7b) *(u64 *)(r1 +16) = r2
# invalid bpf_context access off=16 size=8
>From the compiler point of view it does look like a correct thing
to do, so let's support it on the kernel side.
Credit to Andrii Nakryiko for a proper implementation of
bpf_ctx_wide_store_ok.
Cc: Andrii Nakryiko <andriin@...com>
Cc: Yonghong Song <yhs@...com>
Fixes: cd17d7770578 ("bpf/tools: sync bpf.h")
Reported-by: kernel test robot <rong.a.chen@...el.com>
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
include/linux/filter.h | 6 ++++++
net/core/filter.c | 22 ++++++++++++++--------
2 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 340f7d648974..3901007e36f1 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -746,6 +746,12 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default)
return size <= size_default && (size & (size - 1)) == 0;
}
+#define bpf_ctx_wide_store_ok(off, size, type, field) \
+ (size == sizeof(__u64) && \
+ off >= offsetof(type, field) && \
+ off + sizeof(__u64) <= offsetofend(type, field) && \
+ off % sizeof(__u64) == 0)
+
#define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
diff --git a/net/core/filter.c b/net/core/filter.c
index dc8534be12fc..5d33f2146dab 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6849,6 +6849,16 @@ static bool sock_addr_is_valid_access(int off, int size,
if (!bpf_ctx_narrow_access_ok(off, size, size_default))
return false;
} else {
+ if (bpf_ctx_wide_store_ok(off, size,
+ struct bpf_sock_addr,
+ user_ip6))
+ return true;
+
+ if (bpf_ctx_wide_store_ok(off, size,
+ struct bpf_sock_addr,
+ msg_src_ip6))
+ return true;
+
if (size != size_default)
return false;
}
@@ -7689,9 +7699,6 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type,
/* SOCK_ADDR_STORE_NESTED_FIELD_OFF() has semantic similar to
* SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF() but for store operation.
*
- * It doesn't support SIZE argument though since narrow stores are not
- * supported for now.
- *
* In addition it uses Temporary Field TF (member of struct S) as the 3rd
* "register" since two registers available in convert_ctx_access are not
* enough: we can't override neither SRC, since it contains value to store, nor
@@ -7699,7 +7706,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type,
* instructions. But we need a temporary place to save pointer to nested
* structure whose field we want to store to.
*/
-#define SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, OFF, TF) \
+#define SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, SIZE, OFF, TF) \
do { \
int tmp_reg = BPF_REG_9; \
if (si->src_reg == tmp_reg || si->dst_reg == tmp_reg) \
@@ -7710,8 +7717,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type,
offsetof(S, TF)); \
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(S, F), tmp_reg, \
si->dst_reg, offsetof(S, F)); \
- *insn++ = BPF_STX_MEM( \
- BPF_FIELD_SIZEOF(NS, NF), tmp_reg, si->src_reg, \
+ *insn++ = BPF_STX_MEM(SIZE, tmp_reg, si->src_reg, \
bpf_target_off(NS, NF, FIELD_SIZEOF(NS, NF), \
target_size) \
+ OFF); \
@@ -7723,8 +7729,8 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type,
TF) \
do { \
if (type == BPF_WRITE) { \
- SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, OFF, \
- TF); \
+ SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, SIZE, \
+ OFF, TF); \
} else { \
SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF( \
S, NS, F, NF, SIZE, OFF); \
--
2.22.0.410.gd8fdbe21b5-goog
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