linux-kernel - Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <mb61p5xtcyqo5.fsf@kernel.org>
Date: Thu, 11 Jul 2024 14:00:26 +0000
From: Puranjay Mohan <puranjay@...nel.org>
To: Manu Bretelle <chantra@...a.com>, Daniel Borkmann
 <daniel@...earbox.net>, KP Singh <kpsingh@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman
 <eddyz87@...il.com>, Mykola Lysenko <mykolal@...a.com>, Alexei Starovoitov
 <ast@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu
 <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, "John
 Fastabend" <john.fastabend@...il.com>, Stanislav Fomichev <sdf@...gle.com>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Shuah Khan
 <shuah@...nel.org>, "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
 "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Florent
 Revest <revest@...gle.com>
Subject: Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit_sleep

Hi,
I was able find the root cause of this bug and will send a fix soon!

> Unable to handle kernel paging request at virtual address ffff0000c2a80e68

We are running this test on Qemu with '-cpu max', this means 52-bit
virtual addresses are being used.

The trampolines generation code has the following two lines:

		emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
		emit_call((const u64)__bpf_tramp_enter, ctx);

here the address of struct bpf_tramp_image is moved to R0 and passed as
an argument to __bpf_tramp_enter().

emit_addr_mov_i64() assumes that the address passed to it is in the
vmalloc space and uses at most 48 bits. It sets all the remaining bits
to 1.

but struct bpf_tramp_image is allocated using kzalloc() and when 52-bit
VAs are used, its address is not guaranteed to be 48-bit, therefore we
see this bug, where  0xfff[0]0000c2a80e68 is converted to
0xfff[f]0000c2a80e68 when the trampoline is generated.

The fix would be use emit_a64_mov_i64() for moving this address into R0.

Thanks,
Puranjay

Download attachment "signature.asc" of type "application/pgp-signature" (256 bytes)