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bpf: Improve the info.func_info and info.func_info_rec_size behavior 

1) When bpf_dump_raw_ok() == false and the kernel can provide >=1
   func_info to the userspace, the current behavior is setting
   the info.func_info_cnt to 0 instead of setting info.func_info
   to 0.

   It is different from the behavior in jited_func_lens/nr_jited_func_lens,
   jited_ksyms/nr_jited_ksyms...etc.

   This patch fixes it. (i.e. set func_info to 0 instead of
   func_info_cnt to 0 when bpf_dump_raw_ok() == false).

2) When the userspace passed in info.func_info_cnt == 0, the kernel
   will set the expected func_info size back to the
   info.func_info_rec_size.  It is a way for the userspace to learn
   the kernel expected func_info_rec_size introduced in
   commit 838e96904f ("bpf: Introduce bpf_func_info").

   An exception is the kernel expected size is not set when
   func_info is not available for a bpf_prog.  This makes the
   returned info.func_info_rec_size has different values
   depending on the returned value of info.func_info_cnt.

   This patch sets the kernel expected size to info.func_info_rec_size
   independent of the info.func_info_cnt.

3) The current logic only rejects invalid func_info_rec_size if
   func_info_cnt is non zero.  This patch also rejects invalid
   nonzero info.func_info_rec_size and not equal to the kernel
   expected size.

4) Set info.btf_id as long as prog->aux->btf != NULL.  That will
   setup the later copy_to_user() codes look the same as others
   which then easier to understand and maintain.

   prog->aux->btf is not NULL only if prog->aux->func_info_cnt > 0.

   Breaking up info.btf_id from prog->aux->func_info_cnt is needed
   for the later line info patch anyway.

   A similar change is made to bpf_get_prog_name().

Fixes: 838e96904f ("bpf: Introduce bpf_func_info")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Martin KaFai Lau 2018-12-05 17:35:43 -08:00 committed by Alexei Starovoitov
parent 30da46b5dc
commit 7337224fc1
2 changed files with 20 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/bpf/core.c
View File

@ -410,7 +410,7 @@ static void bpf_get_prog_name(const struct bpf_prog *prog, char *sym)
sym = bin2hex(sym, prog->tag, sizeof(prog->tag));
/* prog->aux->name will be ignored if full btf name is available */
if (prog->aux->btf) {
if (prog->aux->func_info_cnt) {
type = btf_type_by_id(prog->aux->btf,
prog->aux->func_info[prog->aux->func_idx].type_id);
func_name = btf_name_by_offset(prog->aux->btf, type->name_off);

44
kernel/bpf/syscall.c
View File

@ -2083,6 +2083,12 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
return -EFAULT;
}
if ((info.func_info_cnt || info.func_info_rec_size) &&
info.func_info_rec_size != sizeof(struct bpf_func_info))
return -EINVAL;
info.func_info_rec_size = sizeof(struct bpf_func_info);
if (!capable(CAP_SYS_ADMIN)) {
info.jited_prog_len = 0;
info.xlated_prog_len = 0;
@ -2226,35 +2232,23 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
}
}
if (prog->aux->btf) {
u32 krec_size = sizeof(struct bpf_func_info);
u32 ucnt, urec_size;
if (prog->aux->btf)
info.btf_id = btf_id(prog->aux->btf);
ucnt = info.func_info_cnt;
info.func_info_cnt = prog->aux->func_info_cnt;
urec_size = info.func_info_rec_size;
info.func_info_rec_size = krec_size;
if (ucnt) {
/* expect passed-in urec_size is what the kernel expects */
if (urec_size != info.func_info_rec_size)
return -EINVAL;
ulen = info.func_info_cnt;
info.func_info_cnt = prog->aux->func_info_cnt;
if (info.func_info_cnt && ulen) {
if (bpf_dump_raw_ok()) {
char __user *user_finfo;
if (bpf_dump_raw_ok()) {
char __user *user_finfo;
user_finfo = u64_to_user_ptr(info.func_info);
ucnt = min_t(u32, info.func_info_cnt, ucnt);
if (copy_to_user(user_finfo, prog->aux->func_info,
krec_size * ucnt))
return -EFAULT;
} else {
info.func_info_cnt = 0;
}
user_finfo = u64_to_user_ptr(info.func_info);
ulen = min_t(u32, info.func_info_cnt, ulen);
if (copy_to_user(user_finfo, prog->aux->func_info,
info.func_info_rec_size * ulen))
return -EFAULT;
} else {
info.func_info = 0;
}
} else {
info.func_info_cnt = 0;
}
done: