Re: [PATCH bpf-next v3 2/4] bpf_trace: support 32-bit kernels in bpf_kprobe_multi_link_attach

On Tue, May 17, 2022 at 12:36 AM Eugene Syromiatnikov esyr@redhat.com 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 | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 9c041be..a93a54f 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2435,16 +2435,12 @@ 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;
  
  

@@ -2454,6 +2450,7 @@ 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;
  
  

@@ -2461,8 +2458,11 @@ 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;
  

•   }
    addrs = kvmalloc(size, GFP_KERNEL);
    if (!addrs)
            return -ENOMEM;
  

@@ -2486,14 +2486,13 @@ 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 = kvmalloc(cookies_size, GFP_KERNEL);
  

same question about consistent use of kvmalloc_array() and delegating all the overflow checks to it?

            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;
            }
  

-- 2.1.4