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

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Message-ID: <20220516230506.GA25374@asgard.redhat.com>
Date:   Tue, 17 May 2022 01:05:06 +0200
From:   Eugene Syromiatnikov <esyr@...hat.com>
To:     Jiri Olsa <jolsa@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org
Subject: [PATCH bpf v2 2/4] bpf_trace: support 32-bit kernels in
 bpf_kprobe_multi_link_attach

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@...hat.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