Re: [PATCH bpf v2 2/4] bpf_trace: support 32-bit kernels in bpf_kprobe_multi_link_attach

On 5/16/22 4:05 PM, Eugene Syromiatnikov wrote:

It seems that there is no reason not to support 32-bit architectures; doing so requires a bit of rework with respect to cookies handling, however, as the current code implicitly assumes that sizeof(long) == sizeof(u64).

Signed-off-by: Eugene Syromiatnikov esyr@redhat.com

kernel/trace/bpf_trace.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index f1d4e68..bf5bcfb 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2406,16 +2406,12 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr struct bpf_link_primer link_primer; void __user *ucookies; unsigned long *addrs;

• u32 flags, cnt, size;

• u32 flags, cnt, size, cookies_size; void __user *uaddrs; u64 *cookies = NULL; void __user *usyms; int err;

• /* no support for 32bit archs yet */
• if (sizeof(u64) != sizeof(void *))

• return -EOPNOTSUPP;
  

• if (prog->expected_attach_type != BPF_TRACE_KPROBE_MULTI) return -EINVAL;

@@ -2425,6 +2421,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr uaddrs = u64_to_user_ptr(attr->link_create.kprobe_multi.addrs); usyms = u64_to_user_ptr(attr->link_create.kprobe_multi.syms);

• ucookies = u64_to_user_ptr(attr->link_create.kprobe_multi.cookies); if (!!uaddrs == !!usyms) return -EINVAL;

@@ -2432,8 +2429,11 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr if (!cnt) return -EINVAL;

• if (check_mul_overflow(cnt, (u32)sizeof(*addrs), &size))

• if (check_mul_overflow(cnt, (u32)sizeof(*addrs), &size) ||

•    (ucookies &&
  

•     check_mul_overflow(cnt, (u32)sizeof(*cookies), &cookies_size))) {
  

  return -EOVERFLOW;
• } size = cnt * sizeof(*addrs);

size has been calculated, no need to calculate again.

addrs = kvmalloc(size, GFP_KERNEL); if (!addrs) @@ -2450,14 +2450,14 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr goto error; }

• ucookies = u64_to_user_ptr(attr->link_create.kprobe_multi.cookies); if (ucookies) {

• cookies = kvmalloc(size, GFP_KERNEL);
  

• cookies_size = cnt * sizeof(*cookies);
  

same for cookies_size.

• cookies = kvmalloc(cookies_size, GFP_KERNEL);
  

  if (!cookies) { err = -ENOMEM; goto error; }

• if (copy_from_user(cookies, ucookies, size)) {
  

• if (copy_from_user(cookies, ucookies, cookies_size)) {
  err = -EFAULT;
  goto error;
  

  }