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| author | Gianluca Borello <g.borello@gmail.com> | 2017-01-09 19:19:48 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-01-09 22:56:27 +0100 |
| commit | f0318d01b694485af9678a4e120328ae3555be6d (patch) | |
| tree | a5346893ba6a94ecab7394d57bbabd730e1bf59f /kernel/bpf | |
| parent | bpf: allow helpers access to map element values (diff) | |
| download | linux-f0318d01b694485af9678a4e120328ae3555be6d.tar.xz linux-f0318d01b694485af9678a4e120328ae3555be6d.zip | |
bpf: allow adjusted map element values to spill
commit 484611357c19 ("bpf: allow access into map value arrays")
introduces the ability to do pointer math inside a map element value via
the PTR_TO_MAP_VALUE_ADJ register type.
The current support doesn't handle the case where a PTR_TO_MAP_VALUE_ADJ
is spilled into the stack, limiting several use cases, especially when
generating bpf code from a compiler.
Handle this case by explicitly enabling the register type
PTR_TO_MAP_VALUE_ADJ to be spilled. Also, make sure that min_value and
max_value are reset just for BPF_LDX operations that don't result in a
restore of a spilled register from stack.
Signed-off-by: Gianluca Borello <g.borello@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b7014606745b..59ed07b9b4ea 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -481,6 +481,13 @@ static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno) regs[regno].max_value = BPF_REGISTER_MAX_RANGE; } +static void mark_reg_unknown_value_and_range(struct bpf_reg_state *regs, + u32 regno) +{ + mark_reg_unknown_value(regs, regno); + reset_reg_range_values(regs, regno); +} + enum reg_arg_type { SRC_OP, /* register is used as source operand */ DST_OP, /* register is used as destination operand */ @@ -532,6 +539,7 @@ static bool is_spillable_regtype(enum bpf_reg_type type) switch (type) { case PTR_TO_MAP_VALUE: case PTR_TO_MAP_VALUE_OR_NULL: + case PTR_TO_MAP_VALUE_ADJ: case PTR_TO_STACK: case PTR_TO_CTX: case PTR_TO_PACKET: @@ -616,7 +624,8 @@ static int check_stack_read(struct bpf_verifier_state *state, int off, int size, } if (value_regno >= 0) /* have read misc data from the stack */ - mark_reg_unknown_value(state->regs, value_regno); + mark_reg_unknown_value_and_range(state->regs, + value_regno); return 0; } } @@ -825,7 +834,8 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, else err = check_map_access(env, regno, off, size); if (!err && t == BPF_READ && value_regno >= 0) - mark_reg_unknown_value(state->regs, value_regno); + mark_reg_unknown_value_and_range(state->regs, + value_regno); } else if (reg->type == PTR_TO_CTX) { enum bpf_reg_type reg_type = UNKNOWN_VALUE; @@ -837,7 +847,8 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, } err = check_ctx_access(env, off, size, t, ®_type); if (!err && t == BPF_READ && value_regno >= 0) { - mark_reg_unknown_value(state->regs, value_regno); + mark_reg_unknown_value_and_range(state->regs, + value_regno); /* note that reg.[id|off|range] == 0 */ state->regs[value_regno].type = reg_type; } @@ -870,7 +881,8 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, } err = check_packet_access(env, regno, off, size); if (!err && t == BPF_READ && value_regno >= 0) - mark_reg_unknown_value(state->regs, value_regno); + mark_reg_unknown_value_and_range(state->regs, + value_regno); } else { verbose("R%d invalid mem access '%s'\n", regno, reg_type_str[reg->type]); @@ -2744,7 +2756,6 @@ static int do_check(struct bpf_verifier_env *env) if (err) return err; - reset_reg_range_values(regs, insn->dst_reg); if (BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) { insn_idx++; |