diff options
| author | David S. Miller | 2017-05-10 11:38:07 -0700 |
|---|---|---|
| committer | David S. Miller | 2017-05-11 14:19:00 -0400 |
| commit | e07b98d9bffe410019dfcf62c3428d4a96c56a2c (patch) | |
| tree | 52a3aede39b1bac6a409586bcdd272d9aa958868 /kernel/bpf/verifier.c | |
| parent | c5fc9692d101d1318b0f53f9f691cd88ac029317 (diff) | |
bpf: Add strict alignment flag for BPF_PROG_LOAD.
Add a new field, "prog_flags", and an initial flag value
BPF_F_STRICT_ALIGNMENT.
When set, the verifier will enforce strict pointer alignment
regardless of the setting of CONFIG_EFFICIENT_UNALIGNED_ACCESS.
The verifier, in this mode, will also use a fixed value of "2" in
place of NET_IP_ALIGN.
This facilitates test cases that will exercise and validate this part
of the verifier even when run on architectures where alignment doesn't
matter.
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index ff2bfe1d656a..e74fb1b87855 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -791,6 +791,7 @@ static bool is_pointer_value(struct bpf_verifier_env *env, int regno) static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, int off, int size, bool strict) { + int ip_align; int reg_off; /* Byte size accesses are always allowed. */ @@ -807,10 +808,14 @@ static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, reg_off += reg->aux_off; } - /* skb->data is NET_IP_ALIGN-ed */ - if ((NET_IP_ALIGN + reg_off + off) % size != 0) { + /* skb->data is NET_IP_ALIGN-ed, but for strict alignment checking + * we force this to 2 which is universally what architectures use + * when they don't set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS. + */ + ip_align = strict ? 2 : NET_IP_ALIGN; + if ((ip_align + reg_off + off) % size != 0) { verbose("misaligned packet access off %d+%d+%d size %d\n", - NET_IP_ALIGN, reg_off, off, size); + ip_align, reg_off, off, size); return -EACCES; } @@ -828,10 +833,11 @@ static int check_val_ptr_alignment(const struct bpf_reg_state *reg, return 0; } -static int check_ptr_alignment(const struct bpf_reg_state *reg, +static int check_ptr_alignment(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int off, int size) { - bool strict = false; + bool strict = env->strict_alignment; if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) strict = true; @@ -873,7 +879,7 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, if (size < 0) return size; - err = check_ptr_alignment(reg, off, size); + err = check_ptr_alignment(env, reg, off, size); if (err) return err; @@ -3568,6 +3574,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) } else { log_level = 0; } + if (attr->prog_flags & BPF_F_STRICT_ALIGNMENT) + env->strict_alignment = true; + else + env->strict_alignment = false; ret = replace_map_fd_with_map_ptr(env); if (ret < 0) @@ -3673,6 +3683,7 @@ int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, mutex_lock(&bpf_verifier_lock); log_level = 0; + env->strict_alignment = false; env->explored_states = kcalloc(env->prog->len, sizeof(struct bpf_verifier_state_list *), |