-
Andrii Nakryiko authored
As discussed in [0], it's dangerous to allow mapping BPF map, that's meant to be frozen and is read-only on BPF program side, because that allows user-space to actually store a writable view to the page even after it is frozen. This is exacerbated by BPF verifier making a strong assumption that contents of such frozen map will remain unchanged. To prevent this, disallow mapping BPF_F_RDONLY_PROG mmap()'able BPF maps as writable, ever. [0] https://lore.kernel.org/bpf/CAEf4BzYGWYhXdp6BJ7_=9OQPJxQpgug080MMjdSB72i9R+5c6g@mail.gmail.com/ Fixes: fc970227 ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY") Suggested-by:
Jann Horn <jannh@google.com> Signed-off-by:
Andrii Nakryiko <andriin@fb.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org> Reviewed-by:
Jann Horn <jannh@google.com> Link: https://lore.kernel.org/bpf/20200519053824.1089415-1-andriin@fb.com
dfeb376d