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bpf: Generalize ptr_or_null regs check

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This check will be reused by an upcoming commit for conditional jump
checks for sockets. Refactor it a bit to simplify the later commit.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Joe Stringer 2018-10-02 13:35:32 -07:00 committed by Daniel Borkmann
parent 9d2be44a7f
commit 840b9615d6
1 changed files with 25 additions and 18 deletions
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43
kernel/bpf/verifier.c
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@ -249,6 +249,11 @@ static bool type_is_pkt_pointer(enum bpf_reg_type type)
type == PTR_TO_PACKET_META;
}
static bool reg_type_may_be_null(enum bpf_reg_type type)
{
return type == PTR_TO_MAP_VALUE_OR_NULL;
}
/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
[NOT_INIT] = "?",
@ -3599,12 +3604,10 @@ static void reg_combine_min_max(struct bpf_reg_state *true_src,
}
}
static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
bool is_null)
static void mark_ptr_or_null_reg(struct bpf_reg_state *reg, u32 id,
bool is_null)
{
struct bpf_reg_state *reg = &regs[regno];
if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) {
if (reg_type_may_be_null(reg->type) && reg->id == id) {
/* Old offset (both fixed and variable parts) should
* have been known-zero, because we don't allow pointer
* arithmetic on pointers that might be NULL.
@ -3617,11 +3620,13 @@ static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
}
if (is_null) {
reg->type = SCALAR_VALUE;
} else if (reg->map_ptr->inner_map_meta) {
reg->type = CONST_PTR_TO_MAP;
reg->map_ptr = reg->map_ptr->inner_map_meta;
} else {
reg->type = PTR_TO_MAP_VALUE;
} else if (reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
if (reg->map_ptr->inner_map_meta) {
reg->type = CONST_PTR_TO_MAP;
reg->map_ptr = reg->map_ptr->inner_map_meta;
} else {
reg->type = PTR_TO_MAP_VALUE;
}
}
/* We don't need id from this point onwards anymore, thus we
* should better reset it, so that state pruning has chances
@ -3634,8 +3639,8 @@ static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
/* The logic is similar to find_good_pkt_pointers(), both could eventually
* be folded together at some point.
*/
static void mark_map_regs(struct bpf_verifier_state *vstate, u32 regno,
bool is_null)
static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
bool is_null)
{
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *reg, *regs = state->regs;
@ -3643,14 +3648,14 @@ static void mark_map_regs(struct bpf_verifier_state *vstate, u32 regno,
int i, j;
for (i = 0; i < MAX_BPF_REG; i++)
mark_map_reg(regs, i, id, is_null);
mark_ptr_or_null_reg(&regs[i], id, is_null);
for (j = 0; j <= vstate->curframe; j++) {
state = vstate->frame[j];
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
mark_map_reg(&state->stack[i].spilled_ptr, 0, id, is_null);
mark_ptr_or_null_reg(reg, id, is_null);
}
}
}
@ -3852,12 +3857,14 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
/* detect if R == 0 where R is returned from bpf_map_lookup_elem() */
if (BPF_SRC(insn->code) == BPF_K &&
insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
/* Mark all identical map registers in each branch as either
reg_type_may_be_null(dst_reg->type)) {
/* Mark all identical registers in each branch as either
* safe or unknown depending R == 0 or R != 0 conditional.
*/
mark_map_regs(this_branch, insn->dst_reg, opcode == BPF_JNE);
mark_map_regs(other_branch, insn->dst_reg, opcode == BPF_JEQ);
mark_ptr_or_null_regs(this_branch, insn->dst_reg,
opcode == BPF_JNE);
mark_ptr_or_null_regs(other_branch, insn->dst_reg,
opcode == BPF_JEQ);
} else if (!try_match_pkt_pointers(insn, dst_reg, &regs[insn->src_reg],
this_branch, other_branch) &&
is_pointer_value(env, insn->dst_reg)) {