Messages in this thread |  | | Date | Tue, 16 Jan 2024 11:40:53 +0100 | | Subject | Re: [PATCH v2 2/5] crash_dump: save the dm crypt key temporarily | | From | Ondrej Kozina <> |
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On 10/01/2024 08:15, Coiby Xu wrote: > User space is supposed to write the key description to > /sys/kernel/crash_dm_crypt_key so the kernel will read the key and save > a temporary copy for later user. User space has 2 minutes at maximum to > load the kdump initrd before the key gets wiped. And after kdump > retrieves the key, the key will be wiped immediately. > > Signed-off-by: Coiby Xu <coxu@redhat.com> > --- > include/linux/crash_core.h | 7 +- > include/linux/kexec.h | 4 ++ > kernel/Makefile | 2 +- > kernel/crash_dump_dm_crypt.c | 121 +++++++++++++++++++++++++++++++++++ > kernel/ksysfs.c | 23 ++++++- > 5 files changed, 153 insertions(+), 4 deletions(-) > create mode 100644 kernel/crash_dump_dm_crypt.c > > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h > index 5126a4fecb44..7078eda6418d 100644 > --- a/include/linux/crash_core.h > +++ b/include/linux/crash_core.h > @@ -125,6 +125,12 @@ static inline void __init reserve_crashkernel_generic(char *cmdline, > {} > #endif > > +struct kimage; > + > +int crash_sysfs_dm_crypt_key_write(const char *key_des, size_t count); > +int crash_pass_temp_dm_crypt_key(void **addr, unsigned long *sz); > +int crash_load_dm_crypt_key(struct kimage *image); > + > /* Alignment required for elf header segment */ > #define ELF_CORE_HEADER_ALIGN 4096 > > @@ -140,7 +146,6 @@ extern int crash_exclude_mem_range(struct crash_mem *mem, > extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map, > void **addr, unsigned long *sz); > > -struct kimage; > struct kexec_segment; > > #define KEXEC_CRASH_HP_NONE 0 > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > index 6f4626490ebf..bf7ab1e927ef 100644 > --- a/include/linux/kexec.h > +++ b/include/linux/kexec.h > @@ -366,6 +366,10 @@ struct kimage { > void *elf_headers; > unsigned long elf_headers_sz; > unsigned long elf_load_addr; > + > + /* dm crypt key buffer */ > + unsigned long dm_crypt_key_addr; > + unsigned long dm_crypt_key_sz; > }; > > /* kexec interface functions */ > diff --git a/kernel/Makefile b/kernel/Makefile > index 3947122d618b..48859bf63db5 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -119,7 +119,7 @@ obj-$(CONFIG_PERF_EVENTS) += events/ > > obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o > obj-$(CONFIG_PADATA) += padata.o > -obj-$(CONFIG_CRASH_DUMP) += crash_dump.o > +obj-$(CONFIG_CRASH_DUMP) += crash_dump.o crash_dump_dm_crypt.o > obj-$(CONFIG_JUMP_LABEL) += jump_label.o > obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o > obj-$(CONFIG_TORTURE_TEST) += torture.o > diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c > new file mode 100644 > index 000000000000..3a0b0b773598 > --- /dev/null > +++ b/kernel/crash_dump_dm_crypt.c > @@ -0,0 +1,121 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +#include <keys/user-type.h> > +#include <linux/crash_dump.h> > + > +static u8 *dm_crypt_key; > +static unsigned int dm_crypt_key_size; > + > +void wipe_dm_crypt_key(void) > +{ > + if (dm_crypt_key) { > + memset(dm_crypt_key, 0, dm_crypt_key_size * sizeof(u8)); > + kfree(dm_crypt_key); > + dm_crypt_key = NULL; > + } > +} > + > +static void _wipe_dm_crypt_key(struct work_struct *dummy) > +{ > + wipe_dm_crypt_key(); > +} > + > +static DECLARE_DELAYED_WORK(wipe_dm_crypt_key_work, _wipe_dm_crypt_key); > + > +static unsigned __read_mostly wipe_key_delay = 120; /* 2 mins */ > + > +static int crash_save_temp_dm_crypt_key(const char *key_desc, size_t count) > +{ > + const struct user_key_payload *ukp; > + struct key *key; > + > + if (dm_crypt_key) { > + memset(dm_crypt_key, 0, dm_crypt_key_size * sizeof(u8)); > + kfree(dm_crypt_key); > + } > + > + pr_debug("Requesting key %s", key_desc); > + key = request_key(&key_type_user, key_desc, NULL);
If we don't read the key copy form userspace (my reply to top level message) you could use key_type_logon here.
> + > + if (IS_ERR(key)) { > + pr_debug("No such key %s", key_desc); > + return PTR_ERR(key); > + } > + > + ukp = user_key_payload_locked(key); > + if (!ukp) > + return -EKEYREVOKED; > + > + dm_crypt_key = kmalloc(ukp->datalen, GFP_KERNEL); > + if (!dm_crypt_key) > + return -ENOMEM; > + memcpy(dm_crypt_key, ukp->data, ukp->datalen); > + dm_crypt_key_size = ukp->datalen; > + pr_debug("dm crypt key (size=%u): %8ph\n", dm_crypt_key_size, dm_crypt_key); > + schedule_delayed_work(&wipe_dm_crypt_key_work, > + round_jiffies_relative(wipe_key_delay * HZ)); > + return 0; > +} > + > +int crash_sysfs_dm_crypt_key_write(const char *key_desc, size_t count) > +{ > + if (!is_kdump_kernel()) > + return crash_save_temp_dm_crypt_key(key_desc, count); > + return -EINVAL; > +} > +EXPORT_SYMBOL(crash_sysfs_dm_crypt_key_write); > + > +int crash_pass_temp_dm_crypt_key(void **addr, unsigned long *sz) > +{ > + unsigned long dm_crypt_key_sz; > + unsigned char *buf; > + unsigned int *size_ptr; > + > + if (!dm_crypt_key) > + return -EINVAL; > + > + dm_crypt_key_sz = sizeof(unsigned int) + dm_crypt_key_size * sizeof(u8); > + > + buf = vzalloc(dm_crypt_key_sz); > + if (!buf) > + return -ENOMEM; > + > + size_ptr = (unsigned int *)buf; > + memcpy(size_ptr, &dm_crypt_key_size, sizeof(unsigned int)); > + memcpy(size_ptr + 1, dm_crypt_key, dm_crypt_key_size * sizeof(u8)); > + *addr = buf; > + *sz = dm_crypt_key_sz; > + wipe_dm_crypt_key(); > + return 0; > +} > + > +int crash_load_dm_crypt_key(struct kimage *image) > +{ > + int ret; > + struct kexec_buf kbuf = { > + .image = image, > + .buf_min = 0, > + .buf_max = ULONG_MAX, > + .top_down = false, > + .random = true, > + }; > + > + image->dm_crypt_key_addr = 0; > + ret = crash_pass_temp_dm_crypt_key(&kbuf.buffer, &kbuf.bufsz); > + if (ret) > + return ret; > + > + kbuf.memsz = kbuf.bufsz; > + kbuf.buf_align = ELF_CORE_HEADER_ALIGN; > + kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > + ret = kexec_add_buffer(&kbuf); > + if (ret) { > + vfree((void *)kbuf.buffer); > + return ret; > + } > + image->dm_crypt_key_addr = kbuf.mem; > + image->dm_crypt_key_sz = kbuf.bufsz; > + pr_debug("Loaded dm crypt key at 0x%lx bufsz=0x%lx memsz=0x%lx\n", > + image->dm_crypt_key_addr, kbuf.bufsz, kbuf.bufsz); > + > + return ret; > +} > diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c > index 1d4bc493b2f4..f3bb6bc6a604 100644 > --- a/kernel/ksysfs.c > +++ b/kernel/ksysfs.c > @@ -165,16 +165,34 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj, > } > KERNEL_ATTR_RO(vmcoreinfo); > > +static ssize_t crash_dm_crypt_key_show(struct kobject *kobj, > + struct kobj_attribute *attr, > + char *buf) > +{ > + return 0; > +} > + > +static ssize_t crash_dm_crypt_key_store(struct kobject *kobj, > + struct kobj_attribute *attr, > + const char *buf, size_t count) > +{ > + int ret; > + > + ret = crash_sysfs_dm_crypt_key_write(buf, count); > + return ret < 0 ? ret : count; > +} > +KERNEL_ATTR_RW(crash_dm_crypt_key); > + > #ifdef CONFIG_CRASH_HOTPLUG > static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj, > - struct kobj_attribute *attr, char *buf) > + struct kobj_attribute *attr, > + char *buf) > { > unsigned int sz = crash_get_elfcorehdr_size(); > > return sysfs_emit(buf, "%u\n", sz); > } > KERNEL_ATTR_RO(crash_elfcorehdr_size); > - > #endif > > #endif /* CONFIG_CRASH_CORE */ > @@ -267,6 +285,7 @@ static struct attribute * kernel_attrs[] = { > #endif > #ifdef CONFIG_CRASH_CORE > &vmcoreinfo_attr.attr, > + &crash_dm_crypt_key_attr.attr, > #ifdef CONFIG_CRASH_HOTPLUG > &crash_elfcorehdr_size_attr.attr, > #endif
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