linux-kernel - [PATCH bpf] Revert "bpf: program: Refuse non-O_RDWR flags in BPF_OBJ

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Date:   Fri, 18 Jun 2021 03:55:26 -0700
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Maciej Żenczykowski <maze@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Linux Network Development Mailing List <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        BPF Mailing List <bpf@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Greg Kroah-Hartman <gregkh@...gle.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: [PATCH bpf] Revert "bpf: program: Refuse non-O_RDWR flags in BPF_OBJ_GET"

From: Maciej Żenczykowski <maze@...gle.com>

This reverts commit d37300ed182131f1757895a62e556332857417e5.

This breaks Android userspace which expects to be able to
fetch programs with just read permissions.

See: https://cs.android.com/android/platform/superproject/+/master:frameworks/libs/net/common/native/bpf_syscall_wrappers/include/BpfSyscallWrappers.h;drc=7005c764be23d31fa1d69e826b4a2f6689a8c81e;l=124

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Greg Kroah-Hartman <gregkh@...gle.com>
Cc: Lorenz Bauer <lmb@...udflare.com>
Fixes: d37300ed1821 ("bpf: program: Refuse non-O_RDWR flags in BPF_OBJ_GET")
Signed-off-by: Maciej Żenczykowski <maze@...gle.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 b4ebd60a6c16..80da1db47c68 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 = (f_flags != O_RDWR) ? -EINVAL : bpf_prog_new_fd(raw);
+		ret = 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)
-- 
2.32.0.288.g62a8d224e6-goog