From 591fe9888d7809d9ee5c828020b6c6ae27c37229 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 9 Apr 2019 23:20:05 +0200 Subject: bpf: add program side {rd, wr}only support for maps This work adds two new map creation flags BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG in order to allow for read-only or write-only BPF maps from a BPF program side. Today we have BPF_F_RDONLY and BPF_F_WRONLY, but this only applies to system call side, meaning the BPF program has full read/write access to the map as usual while bpf(2) calls with map fd can either only read or write into the map depending on the flags. BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG allows for the exact opposite such that verifier is going to reject program loads if write into a read-only map or a read into a write-only map is detected. For read-only map case also some helpers are forbidden for programs that would alter the map state such as map deletion, update, etc. As opposed to the two BPF_F_RDONLY / BPF_F_WRONLY flags, BPF_F_RDONLY_PROG as well as BPF_F_WRONLY_PROG really do correspond to the map lifetime. We've enabled this generic map extension to various non-special maps holding normal user data: array, hash, lru, lpm, local storage, queue and stack. Further generic map types could be followed up in future depending on use-case. Main use case here is to forbid writes into .rodata map values from verifier side. Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov --- kernel/bpf/syscall.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/bpf/syscall.c') diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 56b4b0e08b3b..0c9276b54c88 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -501,6 +501,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf, map->spin_lock_off = btf_find_spin_lock(btf, value_type); if (map_value_has_spin_lock(map)) { + if (map->map_flags & BPF_F_RDONLY_PROG) + return -EACCES; if (map->map_type != BPF_MAP_TYPE_HASH && map->map_type != BPF_MAP_TYPE_ARRAY && map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE) -- cgit v1.2.3-70-g09d2