6.12-stable review patch. If anyone has any objections, please let me know.
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From: Tao Lyu tao.lyu@epfl.ch
[ Upstream commit 12659d28615d606b36e382f4de2dd05550d202af ]
Currently, KF_ARG_PTR_TO_ITER handling missed checking the reg->type and ensuring it is PTR_TO_STACK. Instead of enforcing this in the caller of process_iter_arg, move the check into it instead so that all callers will gain the check by default. This is similar to process_dynptr_func.
An existing selftest in verifier_bits_iter.c fails due to this change, but it's because it was passing a NULL pointer into iter_next helper and getting an error further down the checks, but probably meant to pass an uninitialized iterator on the stack (as is done in the subsequent test below it). We will gain coverage for non-PTR_TO_STACK arguments in later patches hence just change the declaration to zero-ed stack object.
Fixes: 06accc8779c1 ("bpf: add support for open-coded iterator loops") Suggested-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Tao Lyu tao.lyu@epfl.ch [ Kartikeya: move check into process_iter_arg, rewrite commit log ] Signed-off-by: Kumar Kartikeya Dwivedi memxor@gmail.com Link: https://lore.kernel.org/r/20241203000238.3602922-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 5 +++++ tools/testing/selftests/bpf/progs/verifier_bits_iter.c | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 91317857ea3ee..8955259112c03 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8021,6 +8021,11 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id const struct btf_type *t; int spi, err, i, nr_slots, btf_id;
+ if (reg->type != PTR_TO_STACK) { + verbose(env, "arg#%d expected pointer to an iterator on stack\n", regno - 1); + return -EINVAL; + } + /* For iter_{new,next,destroy} functions, btf_check_iter_kfuncs() * ensures struct convention, so we wouldn't need to do any BTF * validation here. But given iter state can be passed as a parameter diff --git a/tools/testing/selftests/bpf/progs/verifier_bits_iter.c b/tools/testing/selftests/bpf/progs/verifier_bits_iter.c index 7c881bca9af5c..a7a6ae6c162fe 100644 --- a/tools/testing/selftests/bpf/progs/verifier_bits_iter.c +++ b/tools/testing/selftests/bpf/progs/verifier_bits_iter.c @@ -35,9 +35,9 @@ __description("uninitialized iter in ->next()") __failure __msg("expected an initialized iter_bits as arg #1") int BPF_PROG(next_uninit, struct bpf_iter_meta *meta, struct cgroup *cgrp) { - struct bpf_iter_bits *it = NULL; + struct bpf_iter_bits it = {};
- bpf_iter_bits_next(it); + bpf_iter_bits_next(&it); return 0; }