diff options
author | Jakub Sitnicki <jakub@cloudflare.com> | 2022-01-30 14:55:17 +0300 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2022-01-31 23:39:12 +0300 |
commit | 4421a582718ab81608d8486734c18083b822390d (patch) | |
tree | 43a66705d288c67e0c490b8622dad7704f86ab43 /net/core/filter.c | |
parent | b3dddab2ff10853aa3ef70483415d07fee3034ba (diff) | |
download | linux-4421a582718ab81608d8486734c18083b822390d.tar.xz |
bpf: Make dst_port field in struct bpf_sock 16-bit wide
Menglong Dong reports that the documentation for the dst_port field in
struct bpf_sock is inaccurate and confusing. From the BPF program PoV, the
field is a zero-padded 16-bit integer in network byte order. The value
appears to the BPF user as if laid out in memory as so:
offsetof(struct bpf_sock, dst_port) + 0 <port MSB>
+ 8 <port LSB>
+16 0x00
+24 0x00
32-, 16-, and 8-bit wide loads from the field are all allowed, but only if
the offset into the field is 0.
32-bit wide loads from dst_port are especially confusing. The loaded value,
after converting to host byte order with bpf_ntohl(dst_port), contains the
port number in the upper 16-bits.
Remove the confusion by splitting the field into two 16-bit fields. For
backward compatibility, allow 32-bit wide loads from offsetof(struct
bpf_sock, dst_port).
While at it, allow loads 8-bit loads at offset [0] and [1] from dst_port.
Reported-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20220130115518.213259-2-jakub@cloudflare.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'net/core/filter.c')
-rw-r--r-- | net/core/filter.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index a06931c27eeb..99a05199a806 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8265,6 +8265,7 @@ bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, struct bpf_insn_access_aux *info) { const int size_default = sizeof(__u32); + int field_size; if (off < 0 || off >= sizeof(struct bpf_sock)) return false; @@ -8276,7 +8277,6 @@ bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, case offsetof(struct bpf_sock, family): case offsetof(struct bpf_sock, type): case offsetof(struct bpf_sock, protocol): - case offsetof(struct bpf_sock, dst_port): case offsetof(struct bpf_sock, src_port): case offsetof(struct bpf_sock, rx_queue_mapping): case bpf_ctx_range(struct bpf_sock, src_ip4): @@ -8285,6 +8285,14 @@ bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, case bpf_ctx_range_till(struct bpf_sock, dst_ip6[0], dst_ip6[3]): bpf_ctx_record_field_size(info, size_default); return bpf_ctx_narrow_access_ok(off, size, size_default); + case bpf_ctx_range(struct bpf_sock, dst_port): + field_size = size == size_default ? + size_default : sizeof_field(struct bpf_sock, dst_port); + bpf_ctx_record_field_size(info, field_size); + return bpf_ctx_narrow_access_ok(off, size, field_size); + case offsetofend(struct bpf_sock, dst_port) ... + offsetof(struct bpf_sock, dst_ip4) - 1: + return false; } return size == size_default; |