]> git.baikalelectronics.ru Git - kernel.git/commit
bpf: link: Refuse non-O_RDWR flags in BPF_OBJ_GET
authorLorenz Bauer <lmb@cloudflare.com>
Fri, 26 Mar 2021 16:05:00 +0000 (16:05 +0000)
committerAlexei Starovoitov <ast@kernel.org>
Thu, 1 Apr 2021 21:33:14 +0000 (14:33 -0700)
commit25fc94b2f02d832fa8e29419699dcc20b0b05c6a
tree666bd3bc5af6d37d7b02d639b06c9f7db8f984ce
parent06ab134ce8ecfa5a69e850f88f81c8a4c3fa91df
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
kernel/bpf/inode.c