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mm: debug_page_alloc: fix NULL buf in debug_guardpage_minorder_setup To: Ye Liu , Andrew Morton , Vlastimil Babka Cc: Ye Liu , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260806004556.2633049-1-ye.liu@linux.dev> Content-Language: en-US From: John Hubbard In-Reply-To: <20260806004556.2633049-1-ye.liu@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR21CA0014.namprd21.prod.outlook.com (2603:10b6:a03:114::24) To LV3PR12MB9412.namprd12.prod.outlook.com (2603:10b6:408:211::18) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV3PR12MB9412:EE_|PH0PR12MB8821:EE_ X-MS-Office365-Filtering-Correlation-Id: ef1dcbd3-0f50-448a-3ba5-08def3573199 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: 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0kXAXhkvfJ+YDHUVNaunhjzPInSnTDNYuIrLfiFp6DhmtNMgGV7NAwCgEzs35DUqgpKYiZcnoXb3fVue2FNsXUHxXgRn4vGZiPzfono8WSTsa+HNoKCWF1Ossbzrb1byVBIyF1JyjZb+oqpeqNQA3vRGTatEYaHrxLvJzPNoSZ7agnlsngDsQpKBrtYEvx6dg2PZXWgI9wHSd+TKjE8V8Q11zwJBDQU06gDuWO2v5dwuqd/rWzpYw2duDWOnZqUuJVbhgIWjvv2OreP1FJHpIcsc3/U3KSVxdHLOY+rZm1Oqp/mNJCtNHpx8piWtsQsQCz2uMyokGniXM2ZL2lBYYYSh5gI1G2DxEWBZuYpJiIOsDooAQM9gEkwbhhwhUS+B4D6WI7OlInO0d66rtDNeSG0ubMd9YCbSGO9OnIFTQ6gym96VqQ9NWvNjtv7gyVuAoEQCe+spn4ZJEv3E= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/5/26 5:45 PM, Ye Liu wrote: > From: Ye Liu > > If the kernel command line includes "debug_guardpage_minorder" without > an equals sign (i.e., no value is provided), the early parameter > parser passes a NULL buf pointer to the setup function. > > kstrtouint() does not perform a NULL check on its input and calls > directly into kstrtoull() which dereferences s[0] unconditionally, > leading to a NULL pointer dereference and early boot crash. > > Additionally, the error path's pr_err("%s", buf) would also crash with > a NULL format argument. > Maybe a "Fixes:" tag is called for? > Signed-off-by: Ye Liu > --- > mm/debug_page_alloc.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/debug_page_alloc.c b/mm/debug_page_alloc.c > index 41e3d1f1ad96..fd2664c3c86a 100644 > --- a/mm/debug_page_alloc.c > +++ b/mm/debug_page_alloc.c > @@ -22,8 +22,8 @@ static int __init debug_guardpage_minorder_setup(char *buf) > { > unsigned int res; > > - if (kstrtouint(buf, 10, &res) < 0 || res > MAX_PAGE_ORDER / 2) { > - pr_err("Bad debug_guardpage_minorder value: %s\n", buf); > + if (!buf || kstrtouint(buf, 10, &res) < 0 || res > MAX_PAGE_ORDER / 2) { > + pr_err("Bad debug_guardpage_minorder value: %s\n", buf ?: "(missing)"); > return 0; > } > _debug_guardpage_minorder = res; thanks, -- John Hubbard