From patchwork Wed Jun 7 12:39:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Mikityanskiy X-Patchwork-Id: 13270652 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1A14E1426E; Wed, 7 Jun 2023 12:41:08 +0000 (UTC) Received: from mail-ed1-x530.google.com (mail-ed1-x530.google.com [IPv6:2a00:1450:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBB901988; Wed, 7 Jun 2023 05:40:43 -0700 (PDT) Received: by mail-ed1-x530.google.com with SMTP id 4fb4d7f45d1cf-51491b87565so1475729a12.1; Wed, 07 Jun 2023 05:40:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1686141600; x=1688733600; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=pBz2MV4ztkt691mrrB3N7hlq0WVgCYoQcpwdekr5XV0=; b=r2axeMD7pa5eUbn2PSOaNvou4awVkiAgtBMdK05OnUTiPTCNRzbsd93yB5KWdJAJBx aiuEEXNMcyJ57TyABJqi5ZxU734RrU2egayQDci3VyFmGNurNFS1JQ7HLvZQCpU48UqE Ap9kQUa1/6B6ePXRseYcrMLJ1b0vTVlLh2u7cYQFlSuTrpqW2zRceIkVkhxtt/609MxD YrUZfExyl4o8aph+EGVGOEQ5BewO7xJXi6lPvKzfMxt5kZ+P3AvVHuzQ8UCCBYcVDPBC /I+XnERJ3HJbel9+ZQj8JlFFpSO9vaV+pUiWtKsKg4rer9L7QV42hJ9rneqmeSOu2YaJ wwjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686141600; x=1688733600; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=pBz2MV4ztkt691mrrB3N7hlq0WVgCYoQcpwdekr5XV0=; b=cv/gEE7hIzttfpJK+ZSzGESztde3c2/lmm1XcqO9c8BdddnbITBg9y1U7ELFlLc7tZ nTNCAoDKzjM9VL+QE+WgvZaOo5ZEO5dkK2D8ltTP1kKitL7F2z9BlOIrpdjMLO/w4wnP kR/pv+aEJlXY4Vaq8BOpsayFm1zEolqruTj9MBtieI6QK8aIvS9/p1g2XGHUyAmPOCDP 6VZO4f7a+osdZfQrAZOsVeuvBBrPuUBbJ05kBJp0J+rnePuIemcRScTdSeUYaqAqSvUi cGvqI6kEPY6oLjwziogyaZiuGJgvAVEnMlGRKt/kXtGTGDK5pj0O1KmtjsOvYEVKs0Jl +afA== X-Gm-Message-State: AC+VfDw+v9RgtmZp42lfULGoFPl3pzEAFn91rod7+mmaDQrbTCIGqleL /d5t9BIFnqNGymej2JaToRxXNlgp3WXWROW/Rh8= X-Google-Smtp-Source: ACHHUZ6FxDnAxua6geAAvzRbOYl0As0JGMHFLUcojlHJZyN1WrWlLUBxp3/J6donrAgh3Njt7XtM1Q== X-Received: by 2002:aa7:c507:0:b0:50c:3dc:2262 with SMTP id o7-20020aa7c507000000b0050c03dc2262mr3653027edq.39.1686141599613; Wed, 07 Jun 2023 05:39:59 -0700 (PDT) Received: from localhost (tor-exit-48.for-privacy.net. [185.220.101.48]) by smtp.gmail.com with ESMTPSA id c26-20020aa7df1a000000b0051560edc8d4sm6151436edy.45.2023.06.07.05.39.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Jun 2023 05:39:59 -0700 (PDT) From: Maxim Mikityanskiy To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Daniel Borkmann , John Fastabend , Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Maxim Mikityanskiy , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer Subject: [PATCH bpf v4 2/2] selftests/bpf: Add test cases to assert proper ID tracking on spill Date: Wed, 7 Jun 2023 15:39:51 +0300 Message-Id: <20230607123951.558971-3-maxtram95@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230607123951.558971-1-maxtram95@gmail.com> References: <20230607123951.558971-1-maxtram95@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_BL_SPAMCOP_NET,RCVD_IN_DNSWL_NONE, RCVD_IN_SBL_CSS,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Level: ** X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net From: Maxim Mikityanskiy The previous commit fixed a verifier bypass by ensuring that ID is not preserved on narrowing spills. Add the test cases to check the problematic patterns. Signed-off-by: Maxim Mikityanskiy Acked-by: Yonghong Song --- .../selftests/bpf/progs/verifier_spill_fill.c | 79 +++++++++++++++++++ 1 file changed, 79 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c index 136e5530b72c..6115520154e3 100644 --- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c +++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c @@ -371,4 +371,83 @@ __naked void and_then_at_fp_8(void) " ::: __clobber_all); } +SEC("xdp") +__description("32-bit spill of 64-bit reg should clear ID") +__failure __msg("math between ctx pointer and 4294967295 is not allowed") +__naked void spill_32bit_of_64bit_fail(void) +{ + asm volatile (" \ + r6 = r1; \ + /* Roll one bit to force the verifier to track both branches. */\ + call %[bpf_get_prandom_u32]; \ + r0 &= 0x8; \ + /* Put a large number into r1. */ \ + r1 = 0xffffffff; \ + r1 <<= 32; \ + r1 += r0; \ + /* Assign an ID to r1. */ \ + r2 = r1; \ + /* 32-bit spill r1 to stack - should clear the ID! */\ + *(u32*)(r10 - 8) = r1; \ + /* 32-bit fill r2 from stack. */ \ + r2 = *(u32*)(r10 - 8); \ + /* Compare r2 with another register to trigger find_equal_scalars.\ + * Having one random bit is important here, otherwise the verifier cuts\ + * the corners. If the ID was mistakenly preserved on spill, this would\ + * cause the verifier to think that r1 is also equal to zero in one of\ + * the branches, and equal to eight on the other branch.\ + */ \ + r3 = 0; \ + if r2 != r3 goto l0_%=; \ +l0_%=: r1 >>= 32; \ + /* At this point, if the verifier thinks that r1 is 0, an out-of-bounds\ + * read will happen, because it actually contains 0xffffffff.\ + */ \ + r6 += r1; \ + r0 = *(u32*)(r6 + 0); \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +SEC("xdp") +__description("16-bit spill of 32-bit reg should clear ID") +__failure __msg("dereference of modified ctx ptr R6 off=65535 disallowed") +__naked void spill_16bit_of_32bit_fail(void) +{ + asm volatile (" \ + r6 = r1; \ + /* Roll one bit to force the verifier to track both branches. */\ + call %[bpf_get_prandom_u32]; \ + r0 &= 0x8; \ + /* Put a large number into r1. */ \ + w1 = 0xffff0000; \ + r1 += r0; \ + /* Assign an ID to r1. */ \ + r2 = r1; \ + /* 16-bit spill r1 to stack - should clear the ID! */\ + *(u16*)(r10 - 8) = r1; \ + /* 16-bit fill r2 from stack. */ \ + r2 = *(u16*)(r10 - 8); \ + /* Compare r2 with another register to trigger find_equal_scalars.\ + * Having one random bit is important here, otherwise the verifier cuts\ + * the corners. If the ID was mistakenly preserved on spill, this would\ + * cause the verifier to think that r1 is also equal to zero in one of\ + * the branches, and equal to eight on the other branch.\ + */ \ + r3 = 0; \ + if r2 != r3 goto l0_%=; \ +l0_%=: r1 >>= 16; \ + /* At this point, if the verifier thinks that r1 is 0, an out-of-bounds\ + * read will happen, because it actually contains 0xffff.\ + */ \ + r6 += r1; \ + r0 = *(u32*)(r6 + 0); \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + char _license[] SEC("license") = "GPL";