From: Nicholas Dudar <main.kalliope@gmail.com> mainline inclusion from mainline-v7.3-rc1 commit ac65c710cc643cbc52b899627577357867249530 category: bugfix bugzilla: 190889 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- check_ptr_to_btf_access() lets program-type btf_struct_access callbacks validate writes before the default BTF access path rejects non-read accesses. That bypasses the read-only policy for untrusted BTF pointers created by helpers such as bpf_rdonly_cast(). Reject non-read accesses through PTR_UNTRUSTED BTF pointers at the common entry point, before the callback branch to handle all cases. Fixes: 282de143ead9 ("bpf: Introduce allocated objects support") Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Reviewed-by: Amery Hung <ameryhung@gmail.com> Conflicts: kernel/bpf/verifier.c [commit 0df1a55afa832f463f9ad68ddc5de92230f1bc8a not backport] Signed-off-by: Chen Yuxi <chenyuxi19@huawei.com> --- kernel/bpf/verifier.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 1f94aaad5575..6a97d0b89e3d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6601,6 +6601,11 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, return -EACCES; } + if (atype != BPF_READ && (type_flag(reg->type) & PTR_UNTRUSTED)) { + verbose(env, "only read is supported\n"); + return -EACCES; + } + if (env->ops->btf_struct_access && !type_is_alloc(reg->type) && atype == BPF_WRITE) { if (!btf_is_kernel(reg->btf)) { verbose(env, "verifier internal error: reg->btf must be kernel btf\n"); @@ -6609,8 +6614,7 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, ret = env->ops->btf_struct_access(&env->log, reg, off, size); } else { /* Writes are permitted with default btf_struct_access for - * program allocated objects (which always have ref_obj_id > 0), - * but not for untrusted PTR_TO_BTF_ID | MEM_ALLOC. + * program allocated objects (which always have id > 0). */ if (atype != BPF_READ && !type_is_ptr_alloc_obj(reg->type)) { verbose(env, "only read is supported\n"); -- 2.34.1