netdev - [PATCH bpf v2 2/2] bpf: program: refuse non-O_RDWR flags in BPF_OBJ

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Message-Id: <20210326160501.46234-2-lmb@cloudflare.com>
Date:   Fri, 26 Mar 2021 16:05:01 +0000
From:   Lorenz Bauer <lmb@...udflare.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org
Cc:     kernel-team@...udflare.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Lorenz Bauer <lmb@...udflare.com>
Subject: [PATCH bpf v2 2/2] bpf: program: refuse non-O_RDWR flags in BPF_OBJ_GET

As for bpf_link, refuse creating a non-O_RDWR fd. Since program fds
currently don't allow modifications this is a precaution, not a
straight up bug fix.

Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
---
 kernel/bpf/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index dc56237d6960..d2de2abec35b 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -543,7 +543,7 @@ int bpf_obj_get_user(const char __user *pathname, int flags)
 		return PTR_ERR(raw);
 
 	if (type == BPF_TYPE_PROG)
-		ret = bpf_prog_new_fd(raw);
+		ret = (f_flags != O_RDWR) ? -EINVAL : bpf_prog_new_fd(raw);
 	else if (type == BPF_TYPE_MAP)
 		ret = bpf_map_new_fd(raw, f_flags);
 	else if (type == BPF_TYPE_LINK)
-- 
2.27.0