Re: FAILED: patch "[PATCH] bpf: Prevent mmap()'ing read-only maps as writable" failed to apply to 5.6-stable tree

[Sasha Levin <sashal@kernel.org>]

On Mon, May 25, 2020 at 04:39:40PM +0200, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 5.6-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From dfeb376dd4cb2c5004aeb625e2475f58a5ff2ea7 Mon Sep 17 00:00:00 2001
>From: Andrii Nakryiko <andriin@fb.com>
>Date: Mon, 18 May 2020 22:38:24 -0700
>Subject: [PATCH] bpf: Prevent mmap()'ing read-only maps as writable
>
>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: fc9702273e2e ("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

I've adjusted context in the selftest update and queued it up.

-- 
Thanks,
Sasha