Re: [PATCH v9 03/10] btf: Handle dynamic pointer parameter in kfuncs
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2022-08-09 22:13:20
Also in:
bpf, keyrings, linux-doc, linux-kselftest, lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On 8/9/22 3:45 PM, Roberto Sassu wrote:
quoted hunk ↗ jump to hunk
Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure that the dynamic pointer is valid and initialized. Cc: Joanne Koong <redacted> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> --- include/linux/bpf_verifier.h | 3 +++ kernel/bpf/btf.c | 17 +++++++++++++++++ kernel/bpf/verifier.c | 4 ++-- 3 files changed, 22 insertions(+), 2 deletions(-)diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 2e3bad8640dc..55876fbdbae2 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h@@ -560,6 +560,9 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state u32 regno); int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, u32 regno, u32 mem_size); +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, + enum bpf_arg_type arg_type); /* this lives here instead of in bpf.h because it needs to dereference tgt_prog */ static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 67dfc728fbf8..17cca396c89f 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c@@ -6363,6 +6363,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, if (is_kfunc) { bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]); + bool arg_dynptr = btf_type_is_struct(ref_t) && + !strcmp(ref_tname, "bpf_dynptr_kern");
For the strcmp(), could we add some BUILD_BUG_ON() if "bpf_dynptr_kern" ever
gets renamed? I played a bit with the below compile-tested toy example. If we
rename foo_bar into something else, we then get:
[...]
CC net/core/dev.o
In file included from <command-line>:
net/core/dev.c: In function ‘net_dev_init’:
net/core/dev.c:11376:25: error: invalid application of ‘sizeof’ to incomplete type ‘struct foo_bar’
11376 | ({ BUILD_BUG_ON(sizeof(struct x) < 0); \
| ^~~~~~
[...]
diff --git a/net/core/dev.c b/net/core/dev.c
index 716df64fcfa5..a2ed271f7ded 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -11368,16 +11368,30 @@ static struct pernet_operations __net_initdata default_device_ops = { * */ +struct foo_bar { + int a; +}; + +#define stringify_struct(x) \ + ({ BUILD_BUG_ON(sizeof(struct x) < 0); \ + __stringify(x); }) + /* * This is called single threaded during boot, so no need * to take the rtnl semaphore. */ static int __init net_dev_init(void) { + const char *ref_tname = "abc"; int i, rc = -ENOMEM; BUG_ON(!dev_boot_phase); + printk("%s\n", stringify_struct(foo_bar)); + + if (!strcmp(ref_tname, stringify_struct(foo_bar))) + goto out; + if (dev_proc_init()) goto out;