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
| ||
|
Message-Id: <20230502165754.16728-1-will@kernel.org> Date: Tue, 2 May 2023 17:57:54 +0100 From: Will Deacon <will@...nel.org> To: bpf@...r.kernel.org Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, Will Deacon <will@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, Krzesimir Nowak <krzesimir@...volk.io>, Yonghong Song <yhs@...com>, Andrey Ignatov <rdna@...com> Subject: [PATCH] bpf: Fix mask generation for 32-bit narrow loads of 64-bit fields A narrow load from a 64-bit context field results in a 64-bit load followed potentially by a 64-bit right-shift and then a bitwise AND operation to extract the relevant data. In the case of a 32-bit access, an immediate mask of 0xffffffff is used to construct a 64-bit BPP_AND operation which then sign-extends the mask value and effectively acts as a glorified no-op. Fix the mask generation so that narrow loads always perform a 32-bit AND operation. Cc: Alexei Starovoitov <ast@...nel.org> Cc: Daniel Borkmann <daniel@...earbox.net> Cc: John Fastabend <john.fastabend@...il.com> Cc: Krzesimir Nowak <krzesimir@...volk.io> Cc: Yonghong Song <yhs@...com> Cc: Andrey Ignatov <rdna@...com> Fixes: 31fd85816dbe ("bpf: permits narrower load from bpf program context fields") Signed-off-by: Will Deacon <will@...nel.org> --- I spotted this while playing around with the JIT on arm64. I can't figure out why 31fd85816dbe special-cases 8-byte ctx fields in the first place, so I fear I may be missing something... kernel/bpf/verifier.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index fbcf5a4e2fcd..5871aa78d01a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -17033,7 +17033,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) insn_buf[cnt++] = BPF_ALU64_IMM(BPF_RSH, insn->dst_reg, shift); - insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg, + insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg, (1ULL << size * 8) - 1); } } -- 2.40.1.495.gc816e09b53d-goog
Powered by blists - more mailing lists