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bpf: allow wide (u64) aligned stores for some fields of bpf_sock_addr 

Since commit cd17d77705 ("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@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Fixes: cd17d77705 ("bpf/tools: sync bpf.h")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Stanislav Fomichev 2019-07-01 10:38:39 -07:00 committed by Daniel Borkmann
parent d2850ce0bd
commit 600c70bad6
3 changed files with 23 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/filter.h
View File

@ -747,6 +747,12 @@ 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)

6
include/uapi/linux/bpf.h
View File

@ -3247,7 +3247,7 @@ struct bpf_sock_addr {
__u32 user_ip4; /* Allows 1,2,4-byte read and 4-byte write.
* Stored in network byte order.
*/
__u32 user_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write.
__u32 user_ip6[4]; /* Allows 1,2,4-byte read and 4,8-byte write.
* Stored in network byte order.
*/
__u32 user_port; /* Allows 4-byte read and write.
@ -3256,10 +3256,10 @@ struct bpf_sock_addr {
__u32 family; /* Allows 4-byte read, but no write */
__u32 type; /* Allows 4-byte read, but no write */
__u32 protocol; /* Allows 4-byte read, but no write */
__u32 msg_src_ip4; /* Allows 1,2,4-byte read an 4-byte write.
__u32 msg_src_ip4; /* Allows 1,2,4-byte read and 4-byte write.
* Stored in network byte order.
*/
__u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write.
__u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read and 4,8-byte write.
* Stored in network byte order.
*/
__bpf_md_ptr(struct bpf_sock *, sk);

22
net/core/filter.c
View File

@ -6890,6 +6890,16 @@ 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;
}
@ -7730,9 +7740,6 @@ 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
@ -7740,7 +7747,7 @@ 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) \
@ -7751,8 +7758,7 @@ 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); \
@ -7764,8 +7770,8 @@ 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); \