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bpf: Prepare prog_test_struct kfuncs for runtime tests

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In an effort to actually test the refcounting logic at runtime, add a
refcount_t member to prog_test_ref_kfunc and use it in selftests to
verify and test the whole logic more exhaustively.

The kfunc calls for prog_test_member do not require runtime refcounting,
as they are only used for verifier selftests, not during runtime
execution. Hence, their implementation now has a WARN_ON_ONCE as it is
not meant to be reachable code at runtime. It is strictly used in tests
triggering failure cases in the verifier. bpf_kfunc_call_memb_release is
called from map free path, since prog_test_member is embedded in map
value for some verifier tests, so we skip WARN_ON_ONCE for it.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220511194654.765705-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-05-12 01:16:52 +05:30 committed by Alexei Starovoitov
parent 5b74c690e1
commit 5cdccadcac
2 changed files with 19 additions and 8 deletions
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23
net/bpf/test_run.c
View File

@ -564,31 +564,36 @@ struct prog_test_ref_kfunc {
int b;
struct prog_test_member memb;
struct prog_test_ref_kfunc *next;
refcount_t cnt;
};
static struct prog_test_ref_kfunc prog_test_struct = {
.a = 42,
.b = 108,
.next = &prog_test_struct,
.cnt = REFCOUNT_INIT(1),
};
noinline struct prog_test_ref_kfunc *
bpf_kfunc_call_test_acquire(unsigned long *scalar_ptr)
{
/* randomly return NULL */
if (get_jiffies_64() % 2)
return NULL;
refcount_inc(&prog_test_struct.cnt);
return &prog_test_struct;
}
noinline struct prog_test_member *
bpf_kfunc_call_memb_acquire(void)
{
return &prog_test_struct.memb;
WARN_ON_ONCE(1);
return NULL;
}
noinline void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p)
{
if (!p)
return;
refcount_dec(&p->cnt);
}
noinline void bpf_kfunc_call_memb_release(struct prog_test_member *p)
@ -597,12 +602,18 @@ noinline void bpf_kfunc_call_memb_release(struct prog_test_member *p)
noinline void bpf_kfunc_call_memb1_release(struct prog_test_member1 *p)
{
WARN_ON_ONCE(1);
}
noinline struct prog_test_ref_kfunc *
bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b)
bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **pp, int a, int b)
{
return &prog_test_struct;
struct prog_test_ref_kfunc *p = READ_ONCE(*pp);
if (!p)
return NULL;
refcount_inc(&p->cnt);
return p;
}
struct prog_test_pass1 {

4
tools/testing/selftests/bpf/verifier/map_kptr.c
View File

@ -212,13 +212,13 @@
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
BPF_EXIT_INSN(),
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 24),
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 32),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.fixup_map_kptr = { 1 },
.result = REJECT,
.errstr = "access beyond struct prog_test_ref_kfunc at off 24 size 8",
.errstr = "access beyond struct prog_test_ref_kfunc at off 32 size 8",
},
{
"map_kptr: unref: inherit PTR_UNTRUSTED on struct walk",