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Commit 389ede06 authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Alexei Starovoitov
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selftests/bpf: tests with delayed read/precision makrs in loop body 

These test cases try to hide read and precision marks from loop
convergence logic: marks would only be assigned on subsequent loop
iterations or after exploring states pushed to env->head stack first.
Without verifier fix to use exact states comparison logic for
iterators convergence these tests (except 'triple_continue') would be
errorneously marked as safe.
Signed-off-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231024000917.12153-5-eddyz87@gmail.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 2793a8b0
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tools/testing/selftests/bpf/progs/iters.c
View file @ 389ede06
......@@ -14,6 +14,13 @@ int my_pid;
int arr[256];
int small_arr[16] SEC(".data.small_arr");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 10);
__type(key, int);
__type(value, int);
} amap SEC(".maps");
#ifdef REAL_TEST
#define MY_PID_GUARD() if (my_pid != (bpf_get_current_pid_tgid() >> 32)) return 0
#else
......@@ -716,4 +723,515 @@ int iter_pass_iter_ptr_to_subprog(const void *ctx)
return 0;
}
SEC("?raw_tp")
__failure
__msg("R1 type=scalar expected=fp")
__naked int delayed_read_mark(void)
{
/* This is equivalent to C program below.
* The call to bpf_iter_num_next() is reachable with r7 values &fp[-16] and 0xdead.
* State with r7=&fp[-16] is visited first and follows r6 != 42 ... continue branch.
* At this point iterator next() call is reached with r7 that has no read mark.
* Loop body with r7=0xdead would only be visited if verifier would decide to continue
* with second loop iteration. Absence of read mark on r7 might affect state
* equivalent logic used for iterator convergence tracking.
*
* r7 = &fp[-16]
* fp[-16] = 0
* r6 = bpf_get_prandom_u32()
* bpf_iter_num_new(&fp[-8], 0, 10)
* while (bpf_iter_num_next(&fp[-8])) {
* r6++
* if (r6 != 42) {
* r7 = 0xdead
* continue;
* }
* bpf_probe_read_user(r7, 8, 0xdeadbeef); // this is not safe
* }
* bpf_iter_num_destroy(&fp[-8])
* return 0
*/
asm volatile (
"r7 = r10;"
"r7 += -16;"
"r0 = 0;"
"*(u64 *)(r7 + 0) = r0;"
"call %[bpf_get_prandom_u32];"
"r6 = r0;"
"r1 = r10;"
"r1 += -8;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"1:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto 2f;"
"r6 += 1;"
"if r6 != 42 goto 3f;"
"r7 = 0xdead;"
"goto 1b;"
"3:"
"r1 = r7;"
"r2 = 8;"
"r3 = 0xdeadbeef;"
"call %[bpf_probe_read_user];"
"goto 1b;"
"2:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r0 = 0;"
"exit;"
:
: __imm(bpf_get_prandom_u32),
__imm(bpf_iter_num_new),
__imm(bpf_iter_num_next),
__imm(bpf_iter_num_destroy),
__imm(bpf_probe_read_user)
: __clobber_all
);
}
SEC("?raw_tp")
__failure
__msg("math between fp pointer and register with unbounded")
__naked int delayed_precision_mark(void)
{
/* This is equivalent to C program below.
* The test is similar to delayed_iter_mark but verifies that incomplete
* precision don't fool verifier.
* The call to bpf_iter_num_next() is reachable with r7 values -16 and -32.
* State with r7=-16 is visited first and follows r6 != 42 ... continue branch.
* At this point iterator next() call is reached with r7 that has no read
* and precision marks.
* Loop body with r7=-32 would only be visited if verifier would decide to continue
* with second loop iteration. Absence of precision mark on r7 might affect state
* equivalent logic used for iterator convergence tracking.
*
* r8 = 0
* fp[-16] = 0
* r7 = -16
* r6 = bpf_get_prandom_u32()
* bpf_iter_num_new(&fp[-8], 0, 10)
* while (bpf_iter_num_next(&fp[-8])) {
* if (r6 != 42) {
* r7 = -32
* r6 = bpf_get_prandom_u32()
* continue;
* }
* r0 = r10
* r0 += r7
* r8 = *(u64 *)(r0 + 0) // this is not safe
* r6 = bpf_get_prandom_u32()
* }
* bpf_iter_num_destroy(&fp[-8])
* return r8
*/
asm volatile (
"r8 = 0;"
"*(u64 *)(r10 - 16) = r8;"
"r7 = -16;"
"call %[bpf_get_prandom_u32];"
"r6 = r0;"
"r1 = r10;"
"r1 += -8;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"1:"
"r1 = r10;"
"r1 += -8;\n"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto 2f;"
"if r6 != 42 goto 3f;"
"r7 = -32;"
"call %[bpf_get_prandom_u32];"
"r6 = r0;"
"goto 1b;\n"
"3:"
"r0 = r10;"
"r0 += r7;"
"r8 = *(u64 *)(r0 + 0);"
"call %[bpf_get_prandom_u32];"
"r6 = r0;"
"goto 1b;\n"
"2:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r0 = r8;"
"exit;"
:
: __imm(bpf_get_prandom_u32),
__imm(bpf_iter_num_new),
__imm(bpf_iter_num_next),
__imm(bpf_iter_num_destroy),
__imm(bpf_probe_read_user)
: __clobber_all
);
}
SEC("?raw_tp")
__failure
__msg("math between fp pointer and register with unbounded")
__flag(BPF_F_TEST_STATE_FREQ)
__naked int loop_state_deps1(void)
{
/* This is equivalent to C program below.
*
* The case turns out to be tricky in a sense that:
* - states with c=-25 are explored only on a second iteration
* of the outer loop;
* - states with read+precise mark on c are explored only on
* second iteration of the inner loop and in a state which
* is pushed to states stack first.
*
* Depending on the details of iterator convergence logic
* verifier might stop states traversal too early and miss
* unsafe c=-25 memory access.
*
* j = iter_new(); // fp[-16]
* a = 0; // r6
* b = 0; // r7
* c = -24; // r8
* while (iter_next(j)) {
* i = iter_new(); // fp[-8]
* a = 0; // r6
* b = 0; // r7
* while (iter_next(i)) {
* if (a == 1) {
* a = 0;
* b = 1;
* } else if (a == 0) {
* a = 1;
* if (random() == 42)
* continue;
* if (b == 1) {
* *(r10 + c) = 7; // this is not safe
* iter_destroy(i);
* iter_destroy(j);
* return;
* }
* }
* }
* iter_destroy(i);
* a = 0;
* b = 0;
* c = -25;
* }
* iter_destroy(j);
* return;
*/
asm volatile (
"r1 = r10;"
"r1 += -16;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"r6 = 0;"
"r7 = 0;"
"r8 = -24;"
"j_loop_%=:"
"r1 = r10;"
"r1 += -16;"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto j_loop_end_%=;"
"r1 = r10;"
"r1 += -8;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"r6 = 0;"
"r7 = 0;"
"i_loop_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto i_loop_end_%=;"
"check_one_r6_%=:"
"if r6 != 1 goto check_zero_r6_%=;"
"r6 = 0;"
"r7 = 1;"
"goto i_loop_%=;"
"check_zero_r6_%=:"
"if r6 != 0 goto i_loop_%=;"
"r6 = 1;"
"call %[bpf_get_prandom_u32];"
"if r0 != 42 goto check_one_r7_%=;"
"goto i_loop_%=;"
"check_one_r7_%=:"
"if r7 != 1 goto i_loop_%=;"
"r0 = r10;"
"r0 += r8;"
"r1 = 7;"
"*(u64 *)(r0 + 0) = r1;"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r1 = r10;"
"r1 += -16;"
"call %[bpf_iter_num_destroy];"
"r0 = 0;"
"exit;"
"i_loop_end_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r6 = 0;"
"r7 = 0;"
"r8 = -25;"
"goto j_loop_%=;"
"j_loop_end_%=:"
"r1 = r10;"
"r1 += -16;"
"call %[bpf_iter_num_destroy];"
"r0 = 0;"
"exit;"
:
: __imm(bpf_get_prandom_u32),
__imm(bpf_iter_num_new),
__imm(bpf_iter_num_next),
__imm(bpf_iter_num_destroy)
: __clobber_all
);
}
SEC("?raw_tp")
__success
__naked int triple_continue(void)
{
/* This is equivalent to C program below.
* High branching factor of the loop body turned out to be
* problematic for one of the iterator convergence tracking
* algorithms explored.
*
* r6 = bpf_get_prandom_u32()
* bpf_iter_num_new(&fp[-8], 0, 10)
* while (bpf_iter_num_next(&fp[-8])) {
* if (bpf_get_prandom_u32() != 42)
* continue;
* if (bpf_get_prandom_u32() != 42)
* continue;
* if (bpf_get_prandom_u32() != 42)
* continue;
* r0 += 0;
* }
* bpf_iter_num_destroy(&fp[-8])
* return 0
*/
asm volatile (
"r1 = r10;"
"r1 += -8;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"loop_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto loop_end_%=;"
"call %[bpf_get_prandom_u32];"
"if r0 != 42 goto loop_%=;"
"call %[bpf_get_prandom_u32];"
"if r0 != 42 goto loop_%=;"
"call %[bpf_get_prandom_u32];"
"if r0 != 42 goto loop_%=;"
"r0 += 0;"
"goto loop_%=;"
"loop_end_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r0 = 0;"
"exit;"
:
: __imm(bpf_get_prandom_u32),
__imm(bpf_iter_num_new),
__imm(bpf_iter_num_next),
__imm(bpf_iter_num_destroy)
: __clobber_all
);
}
SEC("?raw_tp")
__success
__naked int widen_spill(void)
{
/* This is equivalent to C program below.
* The counter is stored in fp[-16], if this counter is not widened
* verifier states representing loop iterations would never converge.
*
* fp[-16] = 0
* bpf_iter_num_new(&fp[-8], 0, 10)
* while (bpf_iter_num_next(&fp[-8])) {
* r0 = fp[-16];
* r0 += 1;
* fp[-16] = r0;
* }
* bpf_iter_num_destroy(&fp[-8])
* return 0
*/
asm volatile (
"r0 = 0;"
"*(u64 *)(r10 - 16) = r0;"
"r1 = r10;"
"r1 += -8;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"loop_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto loop_end_%=;"
"r0 = *(u64 *)(r10 - 16);"
"r0 += 1;"
"*(u64 *)(r10 - 16) = r0;"
"goto loop_%=;"
"loop_end_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r0 = 0;"
"exit;"
:
: __imm(bpf_iter_num_new),
__imm(bpf_iter_num_next),
__imm(bpf_iter_num_destroy)
: __clobber_all
);
}
SEC("raw_tp")
__success
__naked int checkpoint_states_deletion(void)
{
/* This is equivalent to C program below.
*
* int *a, *b, *c, *d, *e, *f;
* int i, sum = 0;
* bpf_for(i, 0, 10) {
* a = bpf_map_lookup_elem(&amap, &i);
* b = bpf_map_lookup_elem(&amap, &i);
* c = bpf_map_lookup_elem(&amap, &i);
* d = bpf_map_lookup_elem(&amap, &i);
* e = bpf_map_lookup_elem(&amap, &i);
* f = bpf_map_lookup_elem(&amap, &i);
* if (a) sum += 1;
* if (b) sum += 1;
* if (c) sum += 1;
* if (d) sum += 1;
* if (e) sum += 1;
* if (f) sum += 1;
* }
* return 0;
*
* The body of the loop spawns multiple simulation paths
* with different combination of NULL/non-NULL information for a/b/c/d/e/f.
* Each combination is unique from states_equal() point of view.
* Explored states checkpoint is created after each iterator next call.
* Iterator convergence logic expects that eventually current state
* would get equal to one of the explored states and thus loop
* exploration would be finished (at-least for a specific path).
* Verifier evicts explored states with high miss to hit ratio
* to to avoid comparing current state with too many explored
* states per instruction.
* This test is designed to "stress test" eviction policy defined using formula:
*
* sl->miss_cnt > sl->hit_cnt * N + N // if true sl->state is evicted
*
* Currently N is set to 64, which allows for 6 variables in this test.
*/
asm volatile (
"r6 = 0;" /* a */
"r7 = 0;" /* b */
"r8 = 0;" /* c */
"*(u64 *)(r10 - 24) = r6;" /* d */
"*(u64 *)(r10 - 32) = r6;" /* e */
"*(u64 *)(r10 - 40) = r6;" /* f */
"r9 = 0;" /* sum */
"r1 = r10;"
"r1 += -8;"
"r2 = 0;"
"r3 = 10;"
"call %[bpf_iter_num_new];"
"loop_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_next];"
"if r0 == 0 goto loop_end_%=;"
"*(u64 *)(r10 - 16) = r0;"
"r1 = %[amap] ll;"
"r2 = r10;"
"r2 += -16;"
"call %[bpf_map_lookup_elem];"
"r6 = r0;"
"r1 = %[amap] ll;"
"r2 = r10;"
"r2 += -16;"
"call %[bpf_map_lookup_elem];"
"r7 = r0;"
"r1 = %[amap] ll;"
"r2 = r10;"
"r2 += -16;"
"call %[bpf_map_lookup_elem];"
"r8 = r0;"
"r1 = %[amap] ll;"
"r2 = r10;"
"r2 += -16;"
"call %[bpf_map_lookup_elem];"
"*(u64 *)(r10 - 24) = r0;"
"r1 = %[amap] ll;"
"r2 = r10;"
"r2 += -16;"
"call %[bpf_map_lookup_elem];"
"*(u64 *)(r10 - 32) = r0;"
"r1 = %[amap] ll;"
"r2 = r10;"
"r2 += -16;"
"call %[bpf_map_lookup_elem];"
"*(u64 *)(r10 - 40) = r0;"
"if r6 == 0 goto +1;"
"r9 += 1;"
"if r7 == 0 goto +1;"
"r9 += 1;"
"if r8 == 0 goto +1;"
"r9 += 1;"
"r0 = *(u64 *)(r10 - 24);"
"if r0 == 0 goto +1;"
"r9 += 1;"
"r0 = *(u64 *)(r10 - 32);"
"if r0 == 0 goto +1;"
"r9 += 1;"
"r0 = *(u64 *)(r10 - 40);"
"if r0 == 0 goto +1;"
"r9 += 1;"
"goto loop_%=;"
"loop_end_%=:"
"r1 = r10;"
"r1 += -8;"
"call %[bpf_iter_num_destroy];"
"r0 = 0;"
"exit;"
:
: __imm(bpf_map_lookup_elem),
__imm(bpf_iter_num_new),
__imm(bpf_iter_num_next),
__imm(bpf_iter_num_destroy),
__imm_addr(amap)
: __clobber_all
);
}
char _license[] SEC("license") = "GPL";
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