On Tue, May 17, 2022 at 12:36 AM Eugene Syromiatnikov <esyr@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> 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
>
