From nobody Fri Dec 19 08:04:45 2025 Received: from frasgout12.his.huawei.com (frasgout12.his.huawei.com [14.137.139.154]) (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 55427273FD for ; Fri, 15 Dec 2023 12:30:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.18.186.29]) by frasgout12.his.huawei.com (SkyGuard) with ESMTP id 4Ss7570v9rz9xFrq for ; Fri, 15 Dec 2023 19:57:47 +0800 (CST) Received: from mail02.huawei.com (unknown [7.182.16.27]) by mail.maildlp.com (Postfix) with ESMTP id 7C8B6140113 for ; Fri, 15 Dec 2023 20:15:08 +0800 (CST) Received: from huaweicloud.com (unknown [10.48.148.243]) by APP2 (Coremail) with SMTP id GxC2BwCnpV86Q3xlRz6QAg--.57272S4; Fri, 15 Dec 2023 13:15:08 +0100 (CET) From: Petr Tesarik To: Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org (open list:USER-MODE LINUX (UML)), linux-kernel@vger.kernel.org (open list) Cc: Roberto Sassu , petr@tesarici.cz, Petr Tesarik Subject: [PATCH 2/2] um: oops on accessing an non-present page in the vmalloc area Date: Fri, 15 Dec 2023 13:14:31 +0100 Message-Id: <20231215121431.680-3-petrtesarik@huaweicloud.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231215121431.680-1-petrtesarik@huaweicloud.com> References: <20231215121431.680-1-petrtesarik@huaweicloud.com> 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 X-CM-TRANSID: GxC2BwCnpV86Q3xlRz6QAg--.57272S4 X-Coremail-Antispam: 1UD129KBjvJXoW7Kw1DWF1rCFyDKFy3tr18Krg_yoW8GF1xpF 43Gw48tr4I9F1Yya9rX3s2vr4xKas5t3W7C3yDJw1Svw1j9a1fZFWfuwnrAw1FvrW8Gayx tayYyryjkw4DGw7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBG14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jryl82xGYIkIc2 x26xkF7I0E14v26r4j6ryUM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1l84 ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UM2AI xVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20x vE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xv r2IYc2Ij64vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7MxkF7I0Ew4C26cxK6c8Ij28Icw CF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j 6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64 vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_ Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0x vEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0pRLqXdUUUUU= X-CM-SenderInfo: hshw23xhvd2x3n6k3tpzhluzxrxghudrp/ Content-Type: text/plain; charset="utf-8" From: Petr Tesarik If a segmentation fault is caused by an address in the vmalloc area, check that the target page is present. Currently, if the kernel hits a guard page the vmalloc area, UML assumes that the fault is caused merely by a stale mapping and will be fixed by flush_tlb_kernel_vm(). Of course, this will not create any mapping for a guard page, so the faulting instruction will cause exactly the same fault when it is executed again, effectively creating a beautiful (but useless) infinite loop. Signed-off-by: Petr Tesarik --- arch/um/kernel/trap.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c index 1124a382fd14..ca9b5fd83c52 100644 --- a/arch/um/kernel/trap.c +++ b/arch/um/kernel/trap.c @@ -214,11 +214,15 @@ unsigned long segv(struct faultinfo fi, unsigned long= ip, int is_user, int err; int is_write =3D FAULT_WRITE(fi); unsigned long address =3D FAULT_ADDRESS(fi); + pte_t *pte; =20 if (!is_user && regs) current->thread.segv_regs =3D container_of(regs, struct pt_regs, regs); =20 if (!is_user && (address >=3D start_vm) && (address < end_vm)) { + pte =3D virt_to_pte(&init_mm, address); + if (!pte_present(*pte)) + page_fault_oops(regs, address, ip); flush_tlb_kernel_vm(); goto out; } --=20 2.34.1