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| author |   Ilya Leoshkevich <iii@linux.ibm.com> | 2019-08-20 17:50:25 +0200 |
|---|---|---|
| committer |   Daniel Borkmann <daniel@iogearbox.net> | 2019-08-24 01:25:41 +0200 |
| commit | 2c238177bd7f4b14bdf7447cc1cd9bb791f147e6 (patch) | |
| tree | c253667d534aaf7c461da0deae37d65c22bfa06a /net/core | |
| parent | bpf: fix use after free in prog symbol exposure (diff) | |
| download | linux-dev-2c238177bd7f4b14bdf7447cc1cd9bb791f147e6.tar.xz linux-dev-2c238177bd7f4b14bdf7447cc1cd9bb791f147e6.zip | |
bpf: allow narrow loads of some sk_reuseport_md fields with offset > 0
test_select_reuseport fails on s390 due to verifier rejecting
test_select_reuseport_kern.o with the following message:
; data_check.eth_protocol = reuse_md->eth_protocol;
18: (69) r1 = *(u16 *)(r6 +22)
invalid bpf_context access off=22 size=2
This is because on big-endian machines casts from __u32 to __u16 are
generated by referencing the respective variable as __u16 with an offset
of 2 (as opposed to 0 on little-endian machines).
The verifier already has all the infrastructure in place to allow such
accesses, it's just that they are not explicitly enabled for
eth_protocol field. Enable them for eth_protocol field by using
bpf_ctx_range instead of offsetof.
Ditto for ip_protocol, bind_inany and len, since they already allow
narrowing, and the same problem can arise when working with them.
Fixes: 2dbb9b9e6df6 ("bpf: Introduce BPF_PROG_TYPE_SK_REUSEPORT")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 7878f918b8c0..4c6a252d4212 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8757,13 +8757,13 @@ sk_reuseport_is_valid_access(int off, int size, return size == size_default; /* Fields that allow narrowing */ - case offsetof(struct sk_reuseport_md, eth_protocol): + case bpf_ctx_range(struct sk_reuseport_md, eth_protocol): if (size < FIELD_SIZEOF(struct sk_buff, protocol)) return false; /* fall through */ - case offsetof(struct sk_reuseport_md, ip_protocol): - case offsetof(struct sk_reuseport_md, bind_inany): - case offsetof(struct sk_reuseport_md, len): + case bpf_ctx_range(struct sk_reuseport_md, ip_protocol): + case bpf_ctx_range(struct sk_reuseport_md, bind_inany): + case bpf_ctx_range(struct sk_reuseport_md, len): bpf_ctx_record_field_size(info, size_default); return bpf_ctx_narrow_access_ok(off, size, size_default); |