bpf: Fix map permissions check

The map_lookup_and_delete_elem() function should check for both FMODE_CAN_WRITE
and FMODE_CAN_READ permissions because it returns a map element to user space.

Fixes: 2b2c3330962b ("bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall")
Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200527185700.14658-5-a.s.protopopov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d13b804ff0453fdd4ad0b83957a47052c9e4b839..2c969a9b90d3b8f7d86c09e1be86e8f926719485 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1472,7 +1472,8 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);
-       if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
+       if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ) ||
+           !(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
                err = -EPERM;
                goto err_put;
        }