diff options
| author | Lorenz Bauer <lmb@cloudflare.com> | 2021-03-26 16:05:00 +0000 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-04-01 14:33:14 -0700 |
| commit | 25fc94b2f02d832fa8e29419699dcc20b0b05c6a (patch) | |
| tree | 666bd3bc5af6d37d7b02d639b06c9f7db8f984ce /kernel/bpf/inode.c | |
| parent | 06ab134ce8ecfa5a69e850f88f81c8a4c3fa91df (diff) | |
bpf: link: Refuse non-O_RDWR flags in BPF_OBJ_GET
Invoking BPF_OBJ_GET on a pinned bpf_link checks the path access
permissions based on file_flags, but the returned fd ignores flags.
This means that any user can acquire a "read-write" fd for a pinned
link with mode 0664 by invoking BPF_OBJ_GET with BPF_F_RDONLY in
file_flags. The fd can be used to invoke BPF_LINK_DETACH, etc.
Fix this by refusing non-O_RDWR flags in BPF_OBJ_GET. This works
because OBJ_GET by default returns a read write mapping and libbpf
doesn't expose a way to override this behaviour for programs
and links.
Fixes: 70ed506c3bbc ("bpf: Introduce pinnable bpf_link abstraction")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210326160501.46234-1-lmb@cloudflare.com
Diffstat (limited to 'kernel/bpf/inode.c')
| -rw-r--r-- | kernel/bpf/inode.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 1576ff331ee4..dc56237d6960 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -547,7 +547,7 @@ int bpf_obj_get_user(const char __user *pathname, int flags) else if (type == BPF_TYPE_MAP) ret = bpf_map_new_fd(raw, f_flags); else if (type == BPF_TYPE_LINK) - ret = bpf_link_new_fd(raw); + ret = (f_flags != O_RDWR) ? -EINVAL : bpf_link_new_fd(raw); else return -ENOENT; |