Previously, the verifier was treating all PTR_TO_STACK registers passed to a helper call as potentially written to by the helper. However, all calls to check_stack_range_initialized() already have precise access type information available.
Rather than treat ACCESS_HELPER as a proxy for BPF_WRITE, pass enum bpf_access_type to check_stack_range_initialized() to more precisely track helper arguments.
One benefit from this precision is that registers tracked as valid spills and passed as a read-only helper argument remain tracked after the call. Rather than being marked STACK_MISC afterwards.
An additional benefit is the verifier logs are also more precise. For this particular error, users will enjoy a slightly clearer message. See included selftest updates for examples.
Acked-by: Eduard Zingerman eddyz87@gmail.com Signed-off-by: Daniel Xu dxu@dxuuu.xyz --- kernel/bpf/verifier.c | 45 +++++++------------ .../testing/selftests/bpf/progs/dynptr_fail.c | 6 +-- .../selftests/bpf/progs/test_global_func10.c | 2 +- .../selftests/bpf/progs/uninit_stack.c | 5 ++- .../bpf/progs/verifier_basic_stack.c | 2 +- .../selftests/bpf/progs/verifier_const_or.c | 4 +- .../progs/verifier_helper_access_var_len.c | 12 ++--- .../selftests/bpf/progs/verifier_int_ptr.c | 2 +- .../selftests/bpf/progs/verifier_mtu.c | 2 +- .../selftests/bpf/progs/verifier_raw_stack.c | 4 +- .../selftests/bpf/progs/verifier_unpriv.c | 2 +- .../selftests/bpf/progs/verifier_var_off.c | 8 ++-- tools/testing/selftests/bpf/verifier/calls.c | 2 +- 13 files changed, 42 insertions(+), 54 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8879977eb9eb..b71858390e65 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5303,7 +5303,7 @@ enum bpf_access_src { static int check_stack_range_initialized(struct bpf_verifier_env *env, int regno, int off, int access_size, bool zero_size_allowed, - enum bpf_access_src type, + enum bpf_access_type type, struct bpf_call_arg_meta *meta);
static struct bpf_reg_state *reg_state(struct bpf_verifier_env *env, int regno) @@ -5336,7 +5336,7 @@ static int check_stack_read_var_off(struct bpf_verifier_env *env, /* Note that we pass a NULL meta, so raw access will not be permitted. */ err = check_stack_range_initialized(env, ptr_regno, off, size, - false, ACCESS_DIRECT, NULL); + false, BPF_READ, NULL); if (err) return err;
@@ -7190,7 +7190,7 @@ static int check_stack_slot_within_bounds(struct bpf_verifier_env *env, static int check_stack_access_within_bounds( struct bpf_verifier_env *env, int regno, int off, int access_size, - enum bpf_access_src src, enum bpf_access_type type) + enum bpf_access_type type) { struct bpf_reg_state *regs = cur_regs(env); struct bpf_reg_state *reg = regs + regno; @@ -7199,10 +7199,7 @@ static int check_stack_access_within_bounds( int err; char *err_extra;
- if (src == ACCESS_HELPER) - /* We don't know if helpers are reading or writing (or both). */ - err_extra = " indirect access to"; - else if (type == BPF_READ) + if (type == BPF_READ) err_extra = " read from"; else err_extra = " write to"; @@ -7420,7 +7417,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
} else if (reg->type == PTR_TO_STACK) { /* Basic bounds checks. */ - err = check_stack_access_within_bounds(env, regno, off, size, ACCESS_DIRECT, t); + err = check_stack_access_within_bounds(env, regno, off, size, t); if (err) return err;
@@ -7640,13 +7637,11 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i static int check_stack_range_initialized( struct bpf_verifier_env *env, int regno, int off, int access_size, bool zero_size_allowed, - enum bpf_access_src type, struct bpf_call_arg_meta *meta) + enum bpf_access_type type, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *reg = reg_state(env, regno); struct bpf_func_state *state = func(env, reg); int err, min_off, max_off, i, j, slot, spi; - char *err_extra = type == ACCESS_HELPER ? " indirect" : ""; - enum bpf_access_type bounds_check_type; /* Some accesses can write anything into the stack, others are * read-only. */ @@ -7657,18 +7652,10 @@ static int check_stack_range_initialized( return -EACCES; }
- if (type == ACCESS_HELPER) { - /* The bounds checks for writes are more permissive than for - * reads. However, if raw_mode is not set, we'll do extra - * checks below. - */ - bounds_check_type = BPF_WRITE; + if (type == BPF_WRITE) clobber = true; - } else { - bounds_check_type = BPF_READ; - } - err = check_stack_access_within_bounds(env, regno, off, access_size, - type, bounds_check_type); + + err = check_stack_access_within_bounds(env, regno, off, access_size, type); if (err) return err;
@@ -7685,8 +7672,8 @@ static int check_stack_range_initialized( char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); - verbose(env, "R%d%s variable offset stack access prohibited for !root, var_off=%s\n", - regno, err_extra, tn_buf); + verbose(env, "R%d variable offset stack access prohibited for !root, var_off=%s\n", + regno, tn_buf); return -EACCES; } /* Only initialized buffer on stack is allowed to be accessed @@ -7767,14 +7754,14 @@ static int check_stack_range_initialized( }
if (tnum_is_const(reg->var_off)) { - verbose(env, "invalid%s read from stack R%d off %d+%d size %d\n", - err_extra, regno, min_off, i - min_off, access_size); + verbose(env, "invalid read from stack R%d off %d+%d size %d\n", + regno, min_off, i - min_off, access_size); } else { char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); - verbose(env, "invalid%s read from stack R%d var_off %s+%d size %d\n", - err_extra, regno, tn_buf, i - min_off, access_size); + verbose(env, "invalid read from stack R%d var_off %s+%d size %d\n", + regno, tn_buf, i - min_off, access_size); } return -EACCES; mark: @@ -7849,7 +7836,7 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, return check_stack_range_initialized( env, regno, reg->off, access_size, - zero_size_allowed, ACCESS_HELPER, meta); + zero_size_allowed, access_type, meta); case PTR_TO_BTF_ID: return check_ptr_to_btf_access(env, regs, regno, reg->off, access_size, BPF_READ, -1); diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index dfd817d0348c..bd8f15229f5c 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -192,7 +192,7 @@ int ringbuf_invalid_api(void *ctx)
/* Can't add a dynptr to a map */ SEC("?raw_tp") -__failure __msg("invalid indirect read from stack") +__failure __msg("invalid read from stack") int add_dynptr_to_map1(void *ctx) { struct bpf_dynptr ptr; @@ -210,7 +210,7 @@ int add_dynptr_to_map1(void *ctx)
/* Can't add a struct with an embedded dynptr to a map */ SEC("?raw_tp") -__failure __msg("invalid indirect read from stack") +__failure __msg("invalid read from stack") int add_dynptr_to_map2(void *ctx) { struct test_info x; @@ -398,7 +398,7 @@ int data_slice_missing_null_check2(void *ctx) * dynptr argument */ SEC("?raw_tp") -__failure __msg("invalid indirect read from stack") +__failure __msg("invalid read from stack") int invalid_helper1(void *ctx) { struct bpf_dynptr ptr; diff --git a/tools/testing/selftests/bpf/progs/test_global_func10.c b/tools/testing/selftests/bpf/progs/test_global_func10.c index 5da001ca57a5..09d027bd3ea8 100644 --- a/tools/testing/selftests/bpf/progs/test_global_func10.c +++ b/tools/testing/selftests/bpf/progs/test_global_func10.c @@ -26,7 +26,7 @@ __noinline int foo(const struct Big *big) }
SEC("cgroup_skb/ingress") -__failure __msg("invalid indirect access to stack") +__failure __msg("invalid read from stack") int global_func10(struct __sk_buff *skb) { const struct Small small = {.x = skb->len }; diff --git a/tools/testing/selftests/bpf/progs/uninit_stack.c b/tools/testing/selftests/bpf/progs/uninit_stack.c index 8a403470e557..046a204c8fc6 100644 --- a/tools/testing/selftests/bpf/progs/uninit_stack.c +++ b/tools/testing/selftests/bpf/progs/uninit_stack.c @@ -70,7 +70,8 @@ __naked int helper_uninit_to_misc(void *ctx) r1 = r10; \ r1 += -128; \ r2 = 32; \ - call %[bpf_trace_printk]; \ + r3 = 0; \ + call %[bpf_probe_read_user]; \ /* Call to dummy() forces print_verifier_state(..., true), \ * thus showing the stack state, matched by __msg(). \ */ \ @@ -79,7 +80,7 @@ __naked int helper_uninit_to_misc(void *ctx) exit; \ " : - : __imm(bpf_trace_printk), + : __imm(bpf_probe_read_user), __imm(dummy) : __clobber_all); } diff --git a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c index 8d77cc5323d3..fb62e09f2114 100644 --- a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c +++ b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c @@ -28,7 +28,7 @@ __naked void stack_out_of_bounds(void) SEC("socket") __description("uninitialized stack1") __success __log_level(4) __msg("stack depth 8") -__failure_unpriv __msg_unpriv("invalid indirect read from stack") +__failure_unpriv __msg_unpriv("invalid read from stack") __naked void uninitialized_stack1(void) { asm volatile (" \ diff --git a/tools/testing/selftests/bpf/progs/verifier_const_or.c b/tools/testing/selftests/bpf/progs/verifier_const_or.c index ba8922b2eebd..68c568c3c3a0 100644 --- a/tools/testing/selftests/bpf/progs/verifier_const_or.c +++ b/tools/testing/selftests/bpf/progs/verifier_const_or.c @@ -25,7 +25,7 @@ __naked void constant_should_keep_constant_type(void)
SEC("tracepoint") __description("constant register |= constant should not bypass stack boundary checks") -__failure __msg("invalid indirect access to stack R1 off=-48 size=58") +__failure __msg("invalid write to stack R1 off=-48 size=58") __naked void not_bypass_stack_boundary_checks_1(void) { asm volatile (" \ @@ -62,7 +62,7 @@ __naked void register_should_keep_constant_type(void)
SEC("tracepoint") __description("constant register |= constant register should not bypass stack boundary checks") -__failure __msg("invalid indirect access to stack R1 off=-48 size=58") +__failure __msg("invalid write to stack R1 off=-48 size=58") __naked void not_bypass_stack_boundary_checks_2(void) { asm volatile (" \ diff --git a/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c b/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c index 50c6b22606f6..f2c54e4d89eb 100644 --- a/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c +++ b/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c @@ -67,7 +67,7 @@ SEC("socket") __description("helper access to variable memory: stack, bitwise AND, zero included") /* in privileged mode reads from uninitialized stack locations are permitted */ __success __failure_unpriv -__msg_unpriv("invalid indirect read from stack R2 off -64+0 size 64") +__msg_unpriv("invalid read from stack R2 off -64+0 size 64") __retval(0) __naked void stack_bitwise_and_zero_included(void) { @@ -100,7 +100,7 @@ __naked void stack_bitwise_and_zero_included(void)
SEC("tracepoint") __description("helper access to variable memory: stack, bitwise AND + JMP, wrong max") -__failure __msg("invalid indirect access to stack R1 off=-64 size=65") +__failure __msg("invalid write to stack R1 off=-64 size=65") __naked void bitwise_and_jmp_wrong_max(void) { asm volatile (" \ @@ -187,7 +187,7 @@ l0_%=: r0 = 0; \
SEC("tracepoint") __description("helper access to variable memory: stack, JMP, bounds + offset") -__failure __msg("invalid indirect access to stack R1 off=-64 size=65") +__failure __msg("invalid write to stack R1 off=-64 size=65") __naked void memory_stack_jmp_bounds_offset(void) { asm volatile (" \ @@ -211,7 +211,7 @@ l0_%=: r0 = 0; \
SEC("tracepoint") __description("helper access to variable memory: stack, JMP, wrong max") -__failure __msg("invalid indirect access to stack R1 off=-64 size=65") +__failure __msg("invalid write to stack R1 off=-64 size=65") __naked void memory_stack_jmp_wrong_max(void) { asm volatile (" \ @@ -260,7 +260,7 @@ SEC("socket") __description("helper access to variable memory: stack, JMP, no min check") /* in privileged mode reads from uninitialized stack locations are permitted */ __success __failure_unpriv -__msg_unpriv("invalid indirect read from stack R2 off -64+0 size 64") +__msg_unpriv("invalid read from stack R2 off -64+0 size 64") __retval(0) __naked void stack_jmp_no_min_check(void) { @@ -750,7 +750,7 @@ SEC("socket") __description("helper access to variable memory: 8 bytes leak") /* in privileged mode reads from uninitialized stack locations are permitted */ __success __failure_unpriv -__msg_unpriv("invalid indirect read from stack R2 off -64+32 size 64") +__msg_unpriv("invalid read from stack R2 off -64+32 size 64") __retval(0) __naked void variable_memory_8_bytes_leak(void) { diff --git a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c index 5f2efb895edb..59e34d558654 100644 --- a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c +++ b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c @@ -96,7 +96,7 @@ __naked void arg_ptr_to_long_misaligned(void)
SEC("cgroup/sysctl") __description("arg pointer to long size < sizeof(long)") -__failure __msg("invalid indirect access to stack R4 off=-4 size=8") +__failure __msg("invalid write to stack R4 off=-4 size=8") __naked void to_long_size_sizeof_long(void) { asm volatile (" \ diff --git a/tools/testing/selftests/bpf/progs/verifier_mtu.c b/tools/testing/selftests/bpf/progs/verifier_mtu.c index 4ccf1ebc42d1..256956ea1ac5 100644 --- a/tools/testing/selftests/bpf/progs/verifier_mtu.c +++ b/tools/testing/selftests/bpf/progs/verifier_mtu.c @@ -8,7 +8,7 @@ SEC("tc/ingress") __description("uninit/mtu: write rejected") __success __caps_unpriv(CAP_BPF|CAP_NET_ADMIN) -__failure_unpriv __msg_unpriv("invalid indirect read from stack") +__failure_unpriv __msg_unpriv("invalid read from stack") int tc_uninit_mtu(struct __sk_buff *ctx) { __u32 mtu; diff --git a/tools/testing/selftests/bpf/progs/verifier_raw_stack.c b/tools/testing/selftests/bpf/progs/verifier_raw_stack.c index 7cc83acac727..c689665e07b9 100644 --- a/tools/testing/selftests/bpf/progs/verifier_raw_stack.c +++ b/tools/testing/selftests/bpf/progs/verifier_raw_stack.c @@ -236,7 +236,7 @@ __naked void load_bytes_spilled_regs_data(void)
SEC("tc") __description("raw_stack: skb_load_bytes, invalid access 1") -__failure __msg("invalid indirect access to stack R3 off=-513 size=8") +__failure __msg("invalid write to stack R3 off=-513 size=8") __naked void load_bytes_invalid_access_1(void) { asm volatile (" \ @@ -255,7 +255,7 @@ __naked void load_bytes_invalid_access_1(void)
SEC("tc") __description("raw_stack: skb_load_bytes, invalid access 2") -__failure __msg("invalid indirect access to stack R3 off=-1 size=8") +__failure __msg("invalid write to stack R3 off=-1 size=8") __naked void load_bytes_invalid_access_2(void) { asm volatile (" \ diff --git a/tools/testing/selftests/bpf/progs/verifier_unpriv.c b/tools/testing/selftests/bpf/progs/verifier_unpriv.c index 7ea535bfbacd..a4a5e2071604 100644 --- a/tools/testing/selftests/bpf/progs/verifier_unpriv.c +++ b/tools/testing/selftests/bpf/progs/verifier_unpriv.c @@ -199,7 +199,7 @@ __naked void pass_pointer_to_helper_function(void) SEC("socket") __description("unpriv: indirectly pass pointer on stack to helper function") __success __failure_unpriv -__msg_unpriv("invalid indirect read from stack R2 off -8+0 size 8") +__msg_unpriv("invalid read from stack R2 off -8+0 size 8") __retval(0) __naked void on_stack_to_helper_function(void) { diff --git a/tools/testing/selftests/bpf/progs/verifier_var_off.c b/tools/testing/selftests/bpf/progs/verifier_var_off.c index c810f4f6f479..1d36d01b746e 100644 --- a/tools/testing/selftests/bpf/progs/verifier_var_off.c +++ b/tools/testing/selftests/bpf/progs/verifier_var_off.c @@ -203,7 +203,7 @@ __naked void stack_write_clobbers_spilled_regs(void)
SEC("sockops") __description("indirect variable-offset stack access, unbounded") -__failure __msg("invalid unbounded variable-offset indirect access to stack R4") +__failure __msg("invalid unbounded variable-offset write to stack R4") __naked void variable_offset_stack_access_unbounded(void) { asm volatile (" \ @@ -236,7 +236,7 @@ l0_%=: r0 = 0; \
SEC("lwt_in") __description("indirect variable-offset stack access, max out of bound") -__failure __msg("invalid variable-offset indirect access to stack R2") +__failure __msg("invalid variable-offset read from stack R2") __naked void access_max_out_of_bound(void) { asm volatile (" \ @@ -269,7 +269,7 @@ __naked void access_max_out_of_bound(void) */ SEC("socket") __description("indirect variable-offset stack access, zero-sized, max out of bound") -__failure __msg("invalid variable-offset indirect access to stack R1") +__failure __msg("invalid variable-offset write to stack R1") __naked void zero_sized_access_max_out_of_bound(void) { asm volatile (" \ @@ -294,7 +294,7 @@ __naked void zero_sized_access_max_out_of_bound(void)
SEC("lwt_in") __description("indirect variable-offset stack access, min out of bound") -__failure __msg("invalid variable-offset indirect access to stack R2") +__failure __msg("invalid variable-offset read from stack R2") __naked void access_min_out_of_bound(void) { asm volatile (" \ diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c index 7afc2619ab14..18596ae0b0c1 100644 --- a/tools/testing/selftests/bpf/verifier/calls.c +++ b/tools/testing/selftests/bpf/verifier/calls.c @@ -2252,7 +2252,7 @@ BPF_EXIT_INSN(), }, .fixup_map_hash_48b = { 7 }, - .errstr_unpriv = "invalid indirect read from stack R2 off -8+0 size 8", + .errstr_unpriv = "invalid read from stack R2 off -8+0 size 8", .result_unpriv = REJECT, /* in privileged mode reads from uninitialized stack locations are permitted */ .result = ACCEPT,