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[81.2.115.145]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47563e0eee5sm6543818f8f.5.2026.06.30.03.42.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2026 03:42:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1782816171; x=1783420971; 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=kjnvV1ZLxwG9+vMGEcYHhz0AxISfHrD4tLW/HUNersQ=; b=pBj+I3Afb6IuUQsHduti64U2WPHr8jqkJ/vQkcV3qcD92NmX96W6SY8IsMbYs9OPXQ qU8rpcgkJKtE/kMM6Uvrr3wkyxF67Ky4W0y2NLopnuOYwcU17NI4EibmoXdrM/MOkQ9D cZRApc/L8EXc7Epx8fwTkAjLf28nrkEY5lESFrkSZWZAm6zu/spcHXoKH0sPzWZ5/hKO ubXBX0rBhjA8uqKVVOQIChxMkQJMuu2sNK0UdTPTpQGgJ3axFoqeYbpK3OIU/+8azDDx nTUeE9qQRRepX/BrpWJ4lXMDclZx2mtEW+4P2XqPN9wSQ6z5zdw/wKHVCz6JQpT2yjUW TCOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782816171; x=1783420971; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=kjnvV1ZLxwG9+vMGEcYHhz0AxISfHrD4tLW/HUNersQ=; b=lAIW9lrSl+197hAIU0tm5N7YJG4bpN0tvecH4jrsZsUKPE8cGo0v3F3gOx/mx9WdsK kV6zZhe8SylG12eLiLJAnJfzNLv+dQq7aFm/iSE8VmJf/0tmzANImVp423AypZ2w9ooV gTF2/o7v12QF/tTKi33+CRRTomonmAJlVU628fR1wRG0lUSDBO0qj2ZMop6cOBykxuGI EW8YAy1DSp7X8v+b19jMnjotB5CnBzjWLFzIUGD6+BStE8J6cUG6sysIQspVJ255241x 4YIO5NwRB9tDRn9RDiAl7K71U4Q7lWXpCKySRVjWMm9jtWqZirKvMGoeuoOAwD/rFaS3 qihA== X-Gm-Message-State: AOJu0YwWdDurGZwIgUhQToErBGeHtbdBpGXghzezHscwvfv9oRzhx3zn FM08lVNnAp1TJvxMlr3l0xDa0vo+asZ0V5WubHNaTQLmsiRbQul66Xj8riYKLxUimHsOwLE1uvh uEqX6 X-Gm-Gg: AfdE7clv0ougOKBbmH/CCxaoay9XVL7uSpmDJCv79o79rFkJK/+byjobhCUVrNuDMx3 VWAA+Q5gT+LlsH0VzUOXqNQmqs4rVfzb8ql3LHW3nhxcUwvxTz/n1VpsdqA8vtW+gij+Yh1j1a9 J5Lq6UspmMDHkni2V20O0CnA6iv4ozwCqzYfmmHgpiz5amzenoPodrfosM6Axk5MfxgbXWorewp r1gf02wOBgpXBbp5XqJQQqN+Q32B07s6bdLEtjFjhFXMuY4QkCrnJKO+xVnlKCZ1/pCrt9YDaRz Cs5ob2FO+YnR+axS+GVDqPL00eYYruE/3rn7yC0ayw6yqmIKZM8Zz3HKW7V4/hmUFaFkPWWuioI PLeFslvNZv06cAb2519nvs5syUEfBCeKQpwKU4RQpySkzOJx5jCby8zbC2NGE9X7hjj3QJOvzXK YWRRTMsSsU5f3FF5th2J8x3Fak/78ojFb1K7Pl4mBLkxGG+hSFzcEJeAmfoxR33VG90habawwfx 1KLYJe39kov07Wn7JVtKEBefI9lzHE1 X-Received: by 2002:a05:600c:4fc4:b0:492:4363:e7d6 with SMTP id 5b1f17b1804b1-493b82c14dbmr45821375e9.37.1782816171242; Tue, 30 Jun 2026 03:42:51 -0700 (PDT) From: Peter Maydell To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, John Snow Subject: [PATCH] hw/ide: Don't divide by zero if guest specifies 0 sectors Date: Tue, 30 Jun 2026 11:42:49 +0100 Message-ID: <20260630104249.2533126-1-peter.maydell@linaro.org> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 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=lists1p.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::32d; envelope-from=peter.maydell@linaro.org; helo=mail-wm1-x32d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, 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: qemu development 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 @linaro.org) X-ZM-MESSAGEID: 1782816216143158500 Content-Type: text/plain; charset="utf-8" In ide_set_sector() if we're using CHS addressing the way we update the drive state involves dividing by (s->heads * s->sectors). These values can be set by the guest using the INITIALIZE DRIVE PARAMETERS command, which means that s->sectors can be 0. (s->heads can't be 0 because the command passes a heads-1 value.) INITIALIZE DRIVE PARAMETERS is specified to not check the input values for validity; instead no error is posted until some other command makes an illegal access. So we have to cope with a 0 divisor here. Special-case s->sectors being zero. Cc: qemu-stable@nongnu.org Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/2399 Signed-off-by: Peter Maydell --- We don't seem to ever actually check that the guest's read/write ops are within the CHS limits it sets with INITIALIZE DRIVE PARAMETERS -- ide_sect_range_ok() only checks against the underlying block device geometry. Maybe we should? Then a zero-sectors misconfig would result in our reporting the error on the read/write as the spec suggests we should. This patch fixes the division-by-zero, at least, though. --- hw/ide/core.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/hw/ide/core.c b/hw/ide/core.c index f78b00220b..b030531534 100644 --- a/hw/ide/core.c +++ b/hw/ide/core.c @@ -646,13 +646,27 @@ void ide_set_sector(IDEState *s, int64_t sector_num) } } else { /* CHS */ - cyl =3D sector_num / (s->heads * s->sectors); - r =3D sector_num % (s->heads * s->sectors); - s->hcyl =3D cyl >> 8; - s->lcyl =3D cyl; - s->select =3D (s->select & ~(ATA_DEV_HS)) | - ((r / s->sectors) & (ATA_DEV_HS)); - s->sector =3D (r % s->sectors) + 1; + if (s->sectors =3D=3D 0) { + /* + * s->sectors is under guest control via INITIALIZE DRIVE + * PARAMETERS and can be 0; this is an error but can't + * be reported at INITIALIZE DRIVE PARAMETERS time so we + * have to cope with the bad value here. + * (s->heads is always at least 1.) + */ + s->hcyl =3D 0; + s->lcyl =3D 0; + s->select =3D s->select & ~(ATA_DEV_HS); + s->sector =3D 1; + } else { + cyl =3D sector_num / (s->heads * s->sectors); + r =3D sector_num % (s->heads * s->sectors); + s->hcyl =3D cyl >> 8; + s->lcyl =3D cyl; + s->select =3D (s->select & ~(ATA_DEV_HS)) | + ((r / s->sectors) & (ATA_DEV_HS)); + s->sector =3D (r % s->sectors) + 1; + } } } =20 --=20 2.43.0