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

Eugene Syromiatnikov
2022-05-16T23:05:42Z

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);
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);
+ 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;
}
--
2.1.4