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Wed, 6 May 2026 16:09:37 +0000 (GMT) Message-ID: <5af6fd0b-0eca-4089-b76c-45dcc4bf01ed@linux.ibm.com> Date: Wed, 6 May 2026 21:39:35 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 8/9] crash_dump: Disallow configfs/crash_dm_crypt_key/reuse if CONFIG_CRASH_HOTPLUG enabled To: Coiby Xu , kexec@lists.infradead.org Cc: Andrew Morton , Baoquan He , Dave Young , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Jonathan Corbet , Shuah Khan , Coiby Xu , "open list:DOCUMENTATION" , open list References: <20260501234342.2518281-1-coiby.xu@gmail.com> <20260501234342.2518281-9-coiby.xu@gmail.com> Content-Language: en-US From: Sourabh Jain In-Reply-To: <20260501234342.2518281-9-coiby.xu@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA2MDE1OCBTYWx0ZWRfX9vEydiAyv6/h bIdaqRP0cDBpnu/Q4rBAsvqMtRuWQM8COohpwlH/id7D0mmgYGrAwzbpuDv7pnjpxnp9l7XNAyn 9I7pJYEK5KpDXo55qI9mDl7w3h4xO+ic3AryzUH0+pcHwDRiYzD/fgnB57Gqp0lW3VfdkceyXJH Rr+Im1H98NPYD4FOq54UUVRg+1Hc0gKR2zt3kmvEqSYcOO4t4cTnsIBLFpJXo18l+pzUizNMf6t OurTJh2WPyLq/oGuoWdWL5FZQtSIZz9m8zWI34MwrN1Db0njffOfRo9xe0QibPfUDiIjfLziG3I 0of6At05X0YaH+UX5kSoAlWfJbjLbQuhGcfIzI7cqiqMKMh6pqnU17ufOUhwupgnrHsPKjz0Rm5 ODAB3+u33Z9aevoUvPlJGNzM2fmPU7Kn8gWAq3nvmvNhZZi+fMWVD9DJ4nPVTF8EXkH7BOBBHAL 5TW45vPLMfsxjKS1p9A== X-Proofpoint-ORIG-GUID: M9zjn8nAJ53d_-FP2PjULB3AD-cpGVm6 X-Proofpoint-GUID: nDB7-9AbbLcAw4vmxN5TmVz8ATWXCOJc X-Authority-Analysis: v=2.4 cv=W7UIkxWk c=1 sm=1 tr=0 ts=69fb67c9 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=pGLkceISAAAA:8 a=FAMLr4mYtRK9mEqtjuQA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-06_01,2026-05-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 spamscore=0 clxscore=1015 phishscore=0 bulkscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605060158 On 02/05/26 05:13, Coiby Xu wrote: > If CONFIG_CRASH_HOTPLUG is enabled, dm-crypt keys saved to reserved > memory will be took care of automatically. Thus it doesn't make sense > to use configfs/crash_dm_crypt_key/reuse. Reserving > image->dm_crypt_keys_addr is also unnecessary. Currently x86_64 and > ppc64le have implemented CONFIG_CRASH_HOTPLUG feature. > > Also update the doc accordingly. Note two doc issues are fixed as well. > > Fixes: 9ebfa8dcaea7 ("crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging") > Signed-off-by: Coiby Xu > --- > Documentation/admin-guide/kdump/kdump.rst | 9 ++++++--- > kernel/crash_dump_dm_crypt.c | 14 +++++++++++--- > 2 files changed, 17 insertions(+), 6 deletions(-) > > diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst > index 7587caadbae1..73f2e9500c60 100644 > --- a/Documentation/admin-guide/kdump/kdump.rst > +++ b/Documentation/admin-guide/kdump/kdump.rst > @@ -577,9 +577,10 @@ with /sys/kernel/config/crash_dm_crypt_keys for setup, > > 1. Tell the first kernel what logon keys are needed to unlock the disk volumes, > # Add key #1 > - mkdir /sys/kernel/config/crash_dm_crypt_keys/7d26b7b4-e342-4d2d-b660-7426b0996720 > + VOL1_UUID=7d26b7b4-e342-4d2d-b660-7426b0996720 > + mkdir /sys/kernel/config/crash_dm_crypt_keys/$VOL1_UUID > # Add key #1's description > - echo cryptsetup:7d26b7b4-e342-4d2d-b660-7426b0996720 > /sys/kernel/config/crash_dm_crypt_keys/description > + echo cryptsetup:$VOL1_UUID > /sys/kernel/config/crash_dm_crypt_keys/$VOL1_UUID/description > > # how many keys do we have now? > cat /sys/kernel/config/crash_dm_crypt_keys/count > @@ -593,7 +594,9 @@ with /sys/kernel/config/crash_dm_crypt_keys for setup, > > # To support CPU/memory hot-plugging, reuse keys already saved to reserved > # memory > - echo true > /sys/kernel/config/crash_dm_crypt_key/reuse > + # Note if CONFIG_CRASH_HOTPLUG is enabled, this API is totally unnecessary > + # thus will be disabled. > + echo true > /sys/kernel/config/crash_dm_crypt_keys/reuse > > 2. Load the dump-capture kernel > > diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c > index 36e51807d94f..7a7cae17f578 100644 > --- a/kernel/crash_dump_dm_crypt.c > +++ b/kernel/crash_dump_dm_crypt.c > @@ -304,6 +304,11 @@ static ssize_t config_keys_reuse_store(struct config_item *item, > bool val; > int r; > > + if (IS_ENABLED(CONFIG_CRASH_HOTPLUG)) { > + pr_info("CONFIG_CRASH_HOTPLUG already enabled"); > + return -EINVAL; > + } > + Deciding this solely at compile time can create issues. For example, the kernel may be built with CONFIG_CRASH_HOTPLUG, but if kexec tool loads the kdump kernel using the kexec_load system call without hotplug support, it can cause problems. It is rare but possible. How about this: #ifdef CONFIG_CRASH_HOTPLUG     if (kexec_crash_image->hotplug_support) { pr_info("crash image is loaded with hotplug support\n");return -EINVAL;     } #endif This code should be placed after validating kexec_crash_image. - Sourabh Jain > if (!kexec_crash_image || !kexec_crash_image->dm_crypt_keys_addr) { > pr_info("dm-crypt keys haven't be saved to crash-reserved memory\n"); > return -EINVAL; > @@ -486,15 +491,18 @@ int crash_load_dm_crypt_keys(struct kimage *image) > void kexec_file_post_load_cleanup_dm_crypt(struct kimage *image) > { > /* > - * For CPU/memory hot-plugging, the kdump image will be reloaded. Prevent > - * keys_header from being cleaned up during unloading when > - * is_dm_key_reused=true > + * For CPU/memory hot-plugging without CONFIG_CRASH_HOTPLUG, the whole kdump > + * image will be reloaded. Prevent keys_header from being cleaned up during > + * unloading when is_dm_key_reused=true > */ > if (!is_dm_key_reused) { > kfree_sensitive(keys_header); > keys_header = NULL; > } > > + if (IS_ENABLED(CONFIG_CRASH_HOTPLUG)) > + image->dm_crypt_keys_addr = 0; > + > if (mutex_is_locked(&config_keys_subsys.su_mutex)) > mutex_unlock(&config_keys_subsys.su_mutex); > }