From nobody Sat Feb 7 15:10:38 2026 Received: from mail-pl1-f171.google.com (mail-pl1-f171.google.com [209.85.214.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93807C147 for ; Thu, 15 Aug 2024 17:09:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723741759; cv=none; b=O3Y2ftTNHv86ZVn6gTjJSQvsKLchixFyrz6Zjd13hrgslfxdORAxlH2osInyONVuRBch9mpOWvReJckqiKokZ+lom2U6KCvVuE3BnrdYoxjPnuYYw7VPKRkyfCQ2H+G2ZWIbF3jn8SgnYNr6Olg5OdwRcscktRSD50GfQU0Y3tM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723741759; c=relaxed/simple; bh=X5L5hwnjmA/iS+JyOjzWx8Qds/xtd74+wB99jhBeUsQ=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=Wh5D9jWzxB4ZBYdPrINAxHDiBJuuTKAGVI0Fylm/MMZcDxvl3/4A4cXsLmy6pRJlmIa369a9Lf1dBl9h0BEwd5UR/OWRRO7gTDxtT/ZXMEpdz2JAvZAzN0QaSaCRnvh0Aczc5K2/twrUFKugKpuw1fvR+PtqscgBsz/y1pyrOuc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ventanamicro.com; spf=pass smtp.mailfrom=ventanamicro.com; dkim=pass (2048-bit key) header.d=ventanamicro.com header.i=@ventanamicro.com header.b=CmMAxUux; arc=none smtp.client-ip=209.85.214.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ventanamicro.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ventanamicro.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ventanamicro.com header.i=@ventanamicro.com header.b="CmMAxUux" Received: by mail-pl1-f171.google.com with SMTP id d9443c01a7336-201fae21398so3884975ad.1 for ; Thu, 15 Aug 2024 10:09:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ventanamicro.com; s=google; t=1723741756; x=1724346556; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=lVJxT5QcdO7Ui6miH35lV51PmIys+9/MJB+dZzASdvk=; b=CmMAxUuxB9TsXBqMO3V8lG4dOvi6Cq4OO8gfz1SzBjxxH/h7V+yVz+u2xuJt8IDDyl m+qPNdvsi6iPe2r6wr8s4BVSDtGMRJ25WTxVznbBX4VwhWqhKWLXD5vWwmr9vyqa99uo y/nQ6TAY2+gpxdr0loAVdGUBUM+E5DrUu6S2u+2NXTkslVqfU6S1JsoB3WOdr6l5DIRv 0VpETlQMvPdFDQ5FZHMke2vBDsBLw1KVA+U+cCQDWn3pyP3/i36F2MMyLiG9A3RQyIT9 EON+mCsTKN8e2rSOV0j6TdyTCjz2fnIYTtjqWTIopWMGVXsoKlzpjb7AfIlE71SAhNCJ lmdg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723741756; x=1724346556; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=lVJxT5QcdO7Ui6miH35lV51PmIys+9/MJB+dZzASdvk=; b=QSsDcDMQYuLv+N7D6ILMpvkRLrf36F7fMo8LwFGsguQtfBARv1WTXQwxAs9A935WMw I0g5E2Eqpe4kTy71Smx9Kit3/bbXmKkaAD02PV04w0O8FxugKVEH8MEKokuzmx694+UK M5xYNJr3gHAdGB2QxH84cnfbxyY+ezjk0sKblZ+YqoV3w3EAhEfnt9qy/FH3Hhpb5zXQ XLCkIFxnv6AE4wnO/NT8BHJSh/P4rf/SyjqljwrkJrcSuq6u6c8Bh/S11ZEPaKG3SZOQ Qk4iulQITURevf9FwRw4Uble9QJnla8qNTB3jfqDErHXtSvLvrvEK8UhxY2Wase2SZfZ SfWw== X-Forwarded-Encrypted: i=1; AJvYcCUdZE8WYLPSJxx/Ez/44aGWG5VW2BfkwZ0B9/m2c8d0IQTNDFLvB9ubphDkbcOp2hypZgQbX2LXxQ8n+0z5E+RcC8DVpsRZwGpBU/Oe X-Gm-Message-State: AOJu0YwV+pm7bUeFAqC/G4gU+O9A9vl/8YbD6g3KVqhmZSprzG9b4dUe xuBmBW1ZN2QW3rBVRl4Vy1KVejJnihg+kpzKUvOWy5AHwdqZ0XNUJbXOfXQxeaw= X-Google-Smtp-Source: AGHT+IEJsKSb7GMBEJwKRJb18oE3FCx/YFCHoyOQ+/rTrCh0U70ekG6XQEIGyKSA9piI909Jdbh/YA== X-Received: by 2002:a17:903:32c8:b0:201:f44d:6f00 with SMTP id d9443c01a7336-20203f51592mr4328345ad.57.1723741755569; Thu, 15 Aug 2024 10:09:15 -0700 (PDT) Received: from anup-ubuntu-vm.localdomain ([223.185.130.49]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-201f03022d9sm12369535ad.25.2024.08.15.10.09.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Aug 2024 10:09:14 -0700 (PDT) From: Anup Patel To: Palmer Dabbelt , Paul Walmsley Cc: Atish Patra , Andrew Jones , Anup Patel , kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Anup Patel Subject: [PATCH] RISC-V: KVM: Don't zero-out PMU snapshot area before freeing data Date: Thu, 15 Aug 2024 22:39:07 +0530 Message-Id: <20240815170907.2792229-1-apatel@ventanamicro.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With the latest Linux-6.11-rc3, the below NULL pointer crash is observed when SBI PMU snapshot is enabled for the guest and the guest is forcefully powered-off. Unable to handle kernel NULL pointer dereference at virtual address 00000= 00000000508 Oops [#1] Modules linked in: kvm CPU: 0 UID: 0 PID: 61 Comm: term-poll Not tainted 6.11.0-rc3-00018-g44d71= 78dd77a #3 Hardware name: riscv-virtio,qemu (DT) epc : __kvm_write_guest_page+0x94/0xa6 [kvm] ra : __kvm_write_guest_page+0x54/0xa6 [kvm] epc : ffffffff01590e98 ra : ffffffff01590e58 sp : ffff8f80001f39b0 gp : ffffffff81512a60 tp : ffffaf80024872c0 t0 : ffffaf800247e000 t1 : 00000000000007e0 t2 : 0000000000000000 s0 : ffff8f80001f39f0 s1 : 00007fff89ac4000 a0 : ffffffff015dd7e8 a1 : 0000000000000086 a2 : 0000000000000000 a3 : ffffaf8000000000 a4 : ffffaf80024882c0 a5 : 0000000000000000 a6 : ffffaf800328d780 a7 : 00000000000001cc s2 : ffffaf800197bd00 s3 : 00000000000828c4 s4 : ffffaf800248c000 s5 : ffffaf800247d000 s6 : 0000000000001000 s7 : 0000000000001000 s8 : 0000000000000000 s9 : 00007fff861fd500 s10: 0000000000000001 s11: 0000000000800000 t3 : 00000000000004d3 t4 : 00000000000004d3 t5 : ffffffff814126e0 t6 : ffffffff81412700 status: 0000000200000120 badaddr: 0000000000000508 cause: 000000000000000d [] __kvm_write_guest_page+0x94/0xa6 [kvm] [] kvm_vcpu_write_guest+0x56/0x90 [kvm] [] kvm_pmu_clear_snapshot_area+0x42/0x7e [kvm] [] kvm_riscv_vcpu_pmu_deinit.part.0+0xe0/0x14e [kvm] [] kvm_riscv_vcpu_pmu_deinit+0x1a/0x24 [kvm] [] kvm_arch_vcpu_destroy+0x28/0x4c [kvm] [] kvm_destroy_vcpus+0x5a/0xda [kvm] [] kvm_arch_destroy_vm+0x14/0x28 [kvm] [] kvm_destroy_vm+0x168/0x2a0 [kvm] [] kvm_put_kvm+0x3c/0x58 [kvm] [] kvm_vm_release+0x22/0x2e [kvm] Clearly, the kvm_vcpu_write_guest() function is crashing because it is being called from kvm_pmu_clear_snapshot_area() upon guest tear down. To address the above issue, simplify the kvm_pmu_clear_snapshot_area() to not zero-out PMU snapshot area from kvm_pmu_clear_snapshot_area() because the guest is anyway being tore down. The kvm_pmu_clear_snapshot_area() is also called when guest changes PMU snapshot area of a VCPU but even in this case the previous PMU snaphsot area must not be zeroed-out because the guest might have reclaimed the pervious PMU snapshot area for some other purpose. Fixes: c2f41ddbcdd7 ("RISC-V: KVM: Implement SBI PMU Snapshot feature") Signed-off-by: Anup Patel --- arch/riscv/kvm/vcpu_pmu.c | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c index bcf41d6e0df0..2707a51b082c 100644 --- a/arch/riscv/kvm/vcpu_pmu.c +++ b/arch/riscv/kvm/vcpu_pmu.c @@ -391,19 +391,9 @@ int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu,= unsigned int csr_num, static void kvm_pmu_clear_snapshot_area(struct kvm_vcpu *vcpu) { struct kvm_pmu *kvpmu =3D vcpu_to_pmu(vcpu); - int snapshot_area_size =3D sizeof(struct riscv_pmu_snapshot_data); =20 - if (kvpmu->sdata) { - if (kvpmu->snapshot_addr !=3D INVALID_GPA) { - memset(kvpmu->sdata, 0, snapshot_area_size); - kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr, - kvpmu->sdata, snapshot_area_size); - } else { - pr_warn("snapshot address invalid\n"); - } - kfree(kvpmu->sdata); - kvpmu->sdata =3D NULL; - } + kfree(kvpmu->sdata); + kvpmu->sdata =3D NULL; kvpmu->snapshot_addr =3D INVALID_GPA; } =20 --=20 2.34.1