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authorAlex Gartrell <agartrell@fb.com>2015-07-24 00:24:40 +0300
committerDavid S. Miller <davem@davemloft.net>2015-07-27 10:54:10 +0300
commit24b4d2abd0bd628f396dada3e915d395cbf459eb (patch)
treeff4993b4c6f7c86b2f325d93d5c944446e5d5c61
parent6ecfdd28c8a6504349ca8501316b1ed3f639ce44 (diff)
downloadlinux-24b4d2abd0bd628f396dada3e915d395cbf459eb.tar.xz
ebpf: Allow dereferences of PTR_TO_STACK registers
mov %rsp, %r1 ; r1 = rsp add $-8, %r1 ; r1 = rsp - 8 store_q $123, -8(%rsp) ; *(u64*)r1 = 123 <- valid store_q $123, (%r1) ; *(u64*)r1 = 123 <- previously invalid mov $0, %r0 exit ; Always need to exit And we'd get the following error: 0: (bf) r1 = r10 1: (07) r1 += -8 2: (7a) *(u64 *)(r10 -8) = 999 3: (7a) *(u64 *)(r1 +0) = 999 R1 invalid mem access 'fp' Unable to load program We already know that a register is a stack address and the appropriate offset, so we should be able to validate those references as well. Signed-off-by: Alex Gartrell <agartrell@fb.com> Acked-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--kernel/bpf/verifier.c6
-rw-r--r--samples/bpf/test_verifier.c59
2 files changed, 64 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 039d866fd36a..cd307df98cb3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -648,6 +648,9 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off,
struct verifier_state *state = &env->cur_state;
int size, err = 0;
+ if (state->regs[regno].type == PTR_TO_STACK)
+ off += state->regs[regno].imm;
+
size = bpf_size_to_bytes(bpf_size);
if (size < 0)
return size;
@@ -667,7 +670,8 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off,
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown_value(state->regs, value_regno);
- } else if (state->regs[regno].type == FRAME_PTR) {
+ } else if (state->regs[regno].type == FRAME_PTR ||
+ state->regs[regno].type == PTR_TO_STACK) {
if (off >= 0 || off < -MAX_BPF_STACK) {
verbose("invalid stack off=%d size=%d\n", off, size);
return -EACCES;
diff --git a/samples/bpf/test_verifier.c b/samples/bpf/test_verifier.c
index 693605997abc..ee0f110c9c54 100644
--- a/samples/bpf/test_verifier.c
+++ b/samples/bpf/test_verifier.c
@@ -822,6 +822,65 @@ static struct bpf_test tests[] = {
.result = ACCEPT,
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
},
+ {
+ "PTR_TO_STACK store/load",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -10),
+ BPF_ST_MEM(BPF_DW, BPF_REG_1, 2, 0xfaceb00c),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 2),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ },
+ {
+ "PTR_TO_STACK store/load - bad alignment on off",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_1, 2, 0xfaceb00c),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 2),
+ BPF_EXIT_INSN(),
+ },
+ .result = REJECT,
+ .errstr = "misaligned access off -6 size 8",
+ },
+ {
+ "PTR_TO_STACK store/load - bad alignment on reg",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -10),
+ BPF_ST_MEM(BPF_DW, BPF_REG_1, 8, 0xfaceb00c),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 8),
+ BPF_EXIT_INSN(),
+ },
+ .result = REJECT,
+ .errstr = "misaligned access off -2 size 8",
+ },
+ {
+ "PTR_TO_STACK store/load - out of bounds low",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -80000),
+ BPF_ST_MEM(BPF_DW, BPF_REG_1, 8, 0xfaceb00c),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 8),
+ BPF_EXIT_INSN(),
+ },
+ .result = REJECT,
+ .errstr = "invalid stack off=-79992 size=8",
+ },
+ {
+ "PTR_TO_STACK store/load - out of bounds high",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_1, 8, 0xfaceb00c),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 8),
+ BPF_EXIT_INSN(),
+ },
+ .result = REJECT,
+ .errstr = "invalid stack off=0 size=8",
+ },
};
static int probe_filter_length(struct bpf_insn *fp)