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-rw-r--r--kernel/bpf/verifier.c82
1 files changed, 64 insertions, 18 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 545b8c45a578..d906775e12c1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1006,7 +1006,13 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
/* ctx accesses must be at a fixed offset, so that we can
* determine what type of data were returned.
*/
- if (!tnum_is_const(reg->var_off)) {
+ if (reg->off) {
+ verbose(env,
+ "dereference of modified ctx ptr R%d off=%d+%d, ctx+const is allowed, ctx+const+const is not\n",
+ regno, reg->off, off - reg->off);
+ return -EACCES;
+ }
+ if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
@@ -1015,7 +1021,6 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
tn_buf, off, size);
return -EACCES;
}
- off += reg->var_off.value;
err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
if (!err && t == BPF_READ && value_regno >= 0) {
/* ctx access returns either a scalar, or a
@@ -2341,12 +2346,15 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
static void find_good_pkt_pointers(struct bpf_verifier_state *state,
struct bpf_reg_state *dst_reg,
- enum bpf_reg_type type)
+ enum bpf_reg_type type,
+ bool range_right_open)
{
struct bpf_reg_state *regs = state->regs, *reg;
+ u16 new_range;
int i;
- if (dst_reg->off < 0)
+ if (dst_reg->off < 0 ||
+ (dst_reg->off == 0 && range_right_open))
/* This doesn't give us any range */
return;
@@ -2357,9 +2365,13 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *state,
*/
return;
- /* LLVM can generate four kind of checks:
+ new_range = dst_reg->off;
+ if (range_right_open)
+ new_range--;
+
+ /* Examples for register markings:
*
- * Type 1/2:
+ * pkt_data in dst register:
*
* r2 = r3;
* r2 += 8;
@@ -2376,7 +2388,7 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *state,
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
- * Type 3/4:
+ * pkt_data in src register:
*
* r2 = r3;
* r2 += 8;
@@ -2394,7 +2406,9 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *state,
* r3=pkt(id=n,off=0,r=0)
*
* Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
- * so that range of bytes [r3, r3 + 8) is safe to access.
+ * or r3=pkt(id=n,off=0,r=8-1), so that range of bytes [r3, r3 + 8)
+ * and [r3, r3 + 8-1) respectively is safe to access depending on
+ * the check.
*/
/* If our ids match, then we must have the same max_value. And we
@@ -2405,14 +2419,14 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *state,
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].type == type && regs[i].id == dst_reg->id)
/* keep the maximum range already checked */
- regs[i].range = max_t(u16, regs[i].range, dst_reg->off);
+ regs[i].range = max(regs[i].range, new_range);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
reg = &state->spilled_regs[i / BPF_REG_SIZE];
if (reg->type == type && reg->id == dst_reg->id)
- reg->range = max_t(u16, reg->range, dst_reg->off);
+ reg->range = max_t(u16, reg->range, new_range);
}
}
@@ -2776,39 +2790,71 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
- find_good_pkt_pointers(this_branch, dst_reg, PTR_TO_PACKET);
+ /* pkt_data' > pkt_end */
+ find_good_pkt_pointers(this_branch, dst_reg,
+ PTR_TO_PACKET, false);
+ } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
+ dst_reg->type == PTR_TO_PACKET_END &&
+ regs[insn->src_reg].type == PTR_TO_PACKET) {
+ /* pkt_end > pkt_data' */
+ find_good_pkt_pointers(other_branch, &regs[insn->src_reg],
+ PTR_TO_PACKET, true);
+ } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT &&
+ dst_reg->type == PTR_TO_PACKET &&
+ regs[insn->src_reg].type == PTR_TO_PACKET_END) {
+ /* pkt_data' < pkt_end */
+ find_good_pkt_pointers(other_branch, dst_reg, PTR_TO_PACKET,
+ true);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT &&
+ dst_reg->type == PTR_TO_PACKET_END &&
+ regs[insn->src_reg].type == PTR_TO_PACKET) {
+ /* pkt_end < pkt_data' */
+ find_good_pkt_pointers(this_branch, &regs[insn->src_reg],
+ PTR_TO_PACKET, false);
+ } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
- find_good_pkt_pointers(other_branch, dst_reg, PTR_TO_PACKET);
+ /* pkt_data' >= pkt_end */
+ find_good_pkt_pointers(this_branch, dst_reg,
+ PTR_TO_PACKET, true);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
+ /* pkt_end >= pkt_data' */
find_good_pkt_pointers(other_branch, &regs[insn->src_reg],
- PTR_TO_PACKET);
+ PTR_TO_PACKET, false);
+ } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE &&
+ dst_reg->type == PTR_TO_PACKET &&
+ regs[insn->src_reg].type == PTR_TO_PACKET_END) {
+ /* pkt_data' <= pkt_end */
+ find_good_pkt_pointers(other_branch, dst_reg,
+ PTR_TO_PACKET, false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
+ /* pkt_end <= pkt_data' */
find_good_pkt_pointers(this_branch, &regs[insn->src_reg],
- PTR_TO_PACKET);
+ PTR_TO_PACKET, true);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
dst_reg->type == PTR_TO_PACKET_META &&
reg_is_init_pkt_pointer(&regs[insn->src_reg], PTR_TO_PACKET)) {
- find_good_pkt_pointers(this_branch, dst_reg, PTR_TO_PACKET_META);
+ find_good_pkt_pointers(this_branch, dst_reg,
+ PTR_TO_PACKET_META, false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT &&
dst_reg->type == PTR_TO_PACKET_META &&
reg_is_init_pkt_pointer(&regs[insn->src_reg], PTR_TO_PACKET)) {
- find_good_pkt_pointers(other_branch, dst_reg, PTR_TO_PACKET_META);
+ find_good_pkt_pointers(other_branch, dst_reg,
+ PTR_TO_PACKET_META, false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
regs[insn->src_reg].type == PTR_TO_PACKET_META) {
find_good_pkt_pointers(other_branch, &regs[insn->src_reg],
- PTR_TO_PACKET_META);
+ PTR_TO_PACKET_META, false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE &&
reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
regs[insn->src_reg].type == PTR_TO_PACKET_META) {
find_good_pkt_pointers(this_branch, &regs[insn->src_reg],
- PTR_TO_PACKET_META);
+ PTR_TO_PACKET_META, false);
} else if (is_pointer_value(env, insn->dst_reg)) {
verbose(env, "R%d pointer comparison prohibited\n",
insn->dst_reg);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.