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[128.178.122.21]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4257c4e1112sm131868035e9.3.2024.07.02.08.58.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jul 2024 08:58:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1719935886; x=1720540686; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=2kKFopujEfbCs6sAOrXHjFuHM3SCJpZnLQdAZV/N9oM=; b=B2mxbzlnkoznr4pxKA2ju+HnzydviWn5rf9fGkLfNcYU49DQDJRhTRJPjt5sbMN9Cf oFW/s3KiVx+AgG3qZh9r7fGkZYU1+FYFqYc4t0meXjfSJ4cQXDg4gN4QAf6G9DO7sZgI 35OUyUf9TnFGXGS/Of/bi1aIdM4lwq7Fwv8JgC7mOnlbZQ9crWnZ3p4ZrmJ2vanupz52 kRHEAwWQgHH0TiFuWecRprgomaTbuXjfqVhgiyRLbgkh04t4iR/Q3TbqrBinpzXqGl08 lOAk6KYK915kvxLajyz+JB+PAoA/JrzfYiydRTnMpljt82jJXThfLyHQUzu197s8B4WK Ajig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719935886; x=1720540686; 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=2kKFopujEfbCs6sAOrXHjFuHM3SCJpZnLQdAZV/N9oM=; b=ll6GL6oXkSSrxLCKyMBCviKQm1KjcxFO047vp7Rxdv9/Mn3yaihjmUXvNNJ+zwDwzg P8Qhnb550S5yfy45iwhzsVbQ9ixSgJ7XWpD13mZ7fRrW/y8SsolYfFJhtA3w5CHY4RfG 2GEfI7PmtLlNQZIv+Q6k5hSHnUYTjSTHcqg9+ZjhMXknNPhU6oYFXp86yvXSGLNBIcPB wRIpttXP0CWj8WRneyIqQmgfbEhb2cJDxKUqKcKUX0eS8aFqRE3uYBcxNv/XgzxUY/WC h1t0jXn6oePbhLucPZL9oyTM8qgrhEVeualojI9kITEdfhSzbrMZsy3Dueawg2V07HYA 6ykA== X-Forwarded-Encrypted: i=1; AJvYcCVCDsXy6Aaki/T5FEANLcJJI/GPa4Lk/lpx3CppnIm3Y7EoBQBxvXBdgvFp+Md3IQ/JPShAZhOze42IDns7p2j4qQL3UVn40p3lcXmolJddpoyj5ilYS50Rh8s= X-Gm-Message-State: AOJu0YzdI4eIJSrC19kIx9icVZ4jfglIyFGe+RBphvyqJzTkhDvyS7rm 4ceK52KH51gBBmKv7olg2+rWJSlbl0bDC7rMqUYregLWsm+Yz7YHvcV21AY= X-Google-Smtp-Source: AGHT+IHmJyMY88vhwwhPb9nj+wesO6g0B+nDOS3dLPhsHZoTB9CJl+zNpdGfeOUn6YtChT0GoJpyyQ== X-Received: by 2002:a05:600c:5486:b0:425:5f86:41bf with SMTP id 5b1f17b1804b1-4257a02118bmr52827425e9.30.1719935886464; Tue, 02 Jul 2024 08:58:06 -0700 (PDT) From: Zheyu Ma To: Peter Maydell , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Paolo Bonzini Cc: Zheyu Ma , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , qemu-arm@nongnu.org, qemu-devel@nongnu.org Subject: [PATCH v3] hw/char/pl011: Avoid division-by-zero in pl011_get_baudrate() Date: Tue, 2 Jul 2024 17:57:52 +0200 Message-Id: <20240702155752.3022007-1-zheyuma97@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::32e; envelope-from=zheyuma97@gmail.com; helo=mail-wm1-x32e.google.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @gmail.com) X-ZM-MESSAGEID: 1719935930450100003 In pl011_get_baudrate(), when we calculate the baudrate we can accidentally divide by zero. This happens because although (as the specification requires) we treat UARTIBRD =3D 0 as invalid, we aren't correctly limiting UARTIBRD and UARTFBRD values to the 16-bit and 6-bit ranges the hardware allows, and so some non-zero values of UARTIBRD can result in a zero divisor. Enforce the correct register field widths on guest writes and on inbound migration to avoid the division by zero. ASAN log: =3D=3D2973125=3D=3DERROR: AddressSanitizer: FPE on unknown address 0x55f726= 29b348 (pc 0x55f72629b348 bp 0x7fffa24d0e00 sp 0x7fffa24d0d60 T0) #0 0x55f72629b348 in pl011_get_baudrate hw/char/pl011.c:255:17 #1 0x55f726298d94 in pl011_trace_baudrate_change hw/char/pl011.c:260:33 #2 0x55f726296fc8 in pl011_write hw/char/pl011.c:378:9 Reproducer: cat << EOF | qemu-system-aarch64 -display \ none -machine accel=3Dqtest, -m 512M -machine realview-pb-a8 -qtest stdio writeq 0x1000b024 0xf8000000 EOF Suggested-by: Philippe Mathieu-Daud=C3=A9 Suggested-by: Peter Maydell Signed-off-by: Zheyu Ma Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- Changes in v3: - Defined masks for UARTIBRD and UARTFBRD to avoid magic numbers. Changes in v2: - Enforce the correct register field widths on writes to both UARTIBRD and UARTFBRD registers. - Mask UARTIBRD to 16 bits and UARTFBRD to 6 bits in the pl011_post_load function to prevent division by zero during inbound migration. --- hw/char/pl011.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/hw/char/pl011.c b/hw/char/pl011.c index 8753b84a84..f8078aa216 100644 --- a/hw/char/pl011.c +++ b/hw/char/pl011.c @@ -87,6 +87,12 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Cha= rdev *chr) #define CR_DTR (1 << 10) #define CR_LBE (1 << 7) =20 +/* Integer Baud Rate Divider, UARTIBRD */ +#define IBRD_MASK 0x3f + +/* Fractional Baud Rate Divider, UARTFBRD */ +#define FBRD_MASK 0xffff + static const unsigned char pl011_id_arm[8] =3D { 0x11, 0x10, 0x14, 0x00, 0x0d, 0xf0, 0x05, 0xb1 }; static const unsigned char pl011_id_luminary[8] =3D @@ -374,11 +380,11 @@ static void pl011_write(void *opaque, hwaddr offset, s->ilpr =3D value; break; case 9: /* UARTIBRD */ - s->ibrd =3D value; + s->ibrd =3D value & IBRD_MASK; pl011_trace_baudrate_change(s); break; case 10: /* UARTFBRD */ - s->fbrd =3D value; + s->fbrd =3D value & FBRD_MASK; pl011_trace_baudrate_change(s); break; case 11: /* UARTLCR_H */ @@ -531,6 +537,9 @@ static int pl011_post_load(void *opaque, int version_id) s->read_pos =3D 0; } =20 + s->ibrd &=3D IBRD_MASK; + s->fbrd &=3D FBRD_MASK; + return 0; } =20 --=20 2.34.1