| Message ID | 20240122183804.3293904-5-tusharsu@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ima: kexec: measure events between kexec load and execute | expand |
On Mon, 2024-01-22 at 10:38 -0800, Tushar Sugandhi wrote: > ima_dump_measurement_list() is called during kexec 'load', which may > result in loss of IMA measurements during kexec soft reboot. It needs > to be called during kexec 'execute'. > > The below changes need to be part of the same patch to ensure this > patch series remains bisect-safe by ensuring the IMA log gets copied over > during kexec soft reboot both before and after this patch. > > Implement ima_update_kexec_buffer() to be called during kexec 'execute'. > Move ima_dump_measurement_list() from ima_add_kexec_buffer() to > ima_update_kexec_buffer(). Make the necessary variables local static to > the file, so that they are accessible during both kexec 'load' - where > the memory is allocated and mapped to a segment in the new Kernel, and > during 'execute' - where the IMA log gets copied over. > > Implement kimage_file_post_load() and ima_kexec_post_load() to be invoked > after the new Kernel image has been loaded for kexec. > ima_kexec_post_load() will map the IMA buffer to a segment in the newly > loaded Kernel. It will also register the reboot notifier_block to trigger > ima_update_kexec_buffer() at exec 'execute'. This defines two new IMA hooks - ima_kexec_post_load() and ima_update_kexec_buffer(). They shouldn't be hidden here in the move of copying the measurement list from kexec load to execute. If "ima_update_kexec_buffer()" was initially defined as a stub function, the infrastructure could be set up ahead of time. This patch could then be limited to just moving the copy from kexec "load" to "execute", by replacing the stub function with the real function. > Modify kexec_file_load() syscall to call kimage_file_post_load() after the > image has been loaded and prepared for kexec. Call it only on kexec soft > reboot and not for KEXEC_FILE_ON_CRASH.
On 1/24/24 08:11, Mimi Zohar wrote: > On Mon, 2024-01-22 at 10:38 -0800, Tushar Sugandhi wrote: >> ima_dump_measurement_list() is called during kexec 'load', which may >> result in loss of IMA measurements during kexec soft reboot. It needs >> to be called during kexec 'execute'. >> >> The below changes need to be part of the same patch to ensure this >> patch series remains bisect-safe by ensuring the IMA log gets copied over >> during kexec soft reboot both before and after this patch. >> >> Implement ima_update_kexec_buffer() to be called during kexec 'execute'. >> Move ima_dump_measurement_list() from ima_add_kexec_buffer() to >> ima_update_kexec_buffer(). Make the necessary variables local static to >> the file, so that they are accessible during both kexec 'load' - where >> the memory is allocated and mapped to a segment in the new Kernel, and >> during 'execute' - where the IMA log gets copied over. >> >> Implement kimage_file_post_load() and ima_kexec_post_load() to be invoked >> after the new Kernel image has been loaded for kexec. >> ima_kexec_post_load() will map the IMA buffer to a segment in the newly >> loaded Kernel. It will also register the reboot notifier_block to trigger >> ima_update_kexec_buffer() at exec 'execute'. > > This defines two new IMA hooks - ima_kexec_post_load() and > ima_update_kexec_buffer(). They shouldn't be hidden here in the move of copying > the measurement list from kexec load to execute. > > If "ima_update_kexec_buffer()" was initially defined as a stub function, the > infrastructure could be set up ahead of time. This patch could then be limited > to just moving the copy from kexec "load" to "execute", by replacing the stub > function with the real function. > Agreed. Making ima_kexec_post_load() and ima_update_kexec_buffer() as stubs/hooks did cross my mind. Thanks for confirming that. I will split this patch (4/7) into two. First will define the stubs, setup the infrastructure. And second will move the copy from 'load' to 'execute'. ~Tushar >> Modify kexec_file_load() syscall to call kimage_file_post_load() after the >> image has been loaded and prepared for kexec. Call it only on kexec soft >> reboot and not for KEXEC_FILE_ON_CRASH. >
diff --git a/include/linux/ima.h b/include/linux/ima.h index 86b57757c7b1..006db20f852d 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -49,6 +49,9 @@ static inline void ima_appraise_parse_cmdline(void) {} #ifdef CONFIG_IMA_KEXEC extern void ima_add_kexec_buffer(struct kimage *image); +extern void ima_kexec_post_load(struct kimage *image); +#else +static inline void ima_kexec_post_load(struct kimage *image) {} #endif #else diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index bf758fd5062c..ee38799ff1a3 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -184,6 +184,11 @@ kimage_validate_signature(struct kimage *image) } #endif +void kimage_file_post_load(struct kimage *image) +{ + ima_kexec_post_load(image); +} + /* * In file mode list of segments is prepared by kernel. Copy relevant * data from user space, do error checking, prepare segment list @@ -399,6 +404,9 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, kimage_terminate(image); + if (!(flags & KEXEC_FILE_ON_CRASH)) + kimage_file_post_load(image); + ret = machine_kexec_post_load(image); if (ret) goto out; diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c index d92a48284cc4..25150bfc7129 100644 --- a/security/integrity/ima/ima_kexec.c +++ b/security/integrity/ima/ima_kexec.c @@ -12,10 +12,15 @@ #include <linux/kexec.h> #include <linux/of.h> #include <linux/ima.h> +#include <linux/reboot.h> +#include <asm/page.h> #include "ima.h" #ifdef CONFIG_IMA_KEXEC static struct seq_file ima_kexec_file; +static void *ima_kexec_buffer; +static size_t kexec_segment_size; +static bool ima_kexec_update_registered; static void ima_free_kexec_file_buf(struct seq_file *sf) { @@ -120,7 +125,6 @@ void ima_add_kexec_buffer(struct kimage *image) /* use more understandable variable names than defined in kbuf */ void *kexec_buffer = NULL; size_t kexec_buffer_size; - size_t kexec_segment_size; int ret; /* @@ -145,14 +149,6 @@ void ima_add_kexec_buffer(struct kimage *image) return; } - ret = ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, - kexec_segment_size); - if (ret < 0) { - pr_err("%s: Failed to dump IMA measurements. Error:%d.\n", - __func__, ret); - return; - } - kbuf.buffer = kexec_buffer; kbuf.bufsz = kexec_buffer_size; kbuf.memsz = kexec_segment_size; @@ -174,6 +170,74 @@ void ima_add_kexec_buffer(struct kimage *image) kbuf.mem); } +/* + * Called during kexec execute so that IMA can update the measurement list. + */ +static int ima_update_kexec_buffer(struct notifier_block *self, + unsigned long action, void *data) +{ + void *buf = NULL; + size_t buf_size; + int ret = NOTIFY_OK; + + if (!kexec_in_progress) { + pr_info("%s: No kexec in progress.\n", __func__); + return ret; + } + + if (!ima_kexec_buffer) { + pr_err("%s: Kexec buffer not set.\n", __func__); + return ret; + } + + ret = ima_dump_measurement_list(&buf_size, &buf, + kexec_segment_size); + + if (!buf) { + pr_err("%s: Dump measurements failed. Error:%d\n", + __func__, ret); + goto out; + } + memcpy(ima_kexec_buffer, buf, buf_size); +out: + kimage_unmap_segment(ima_kexec_buffer); + ima_kexec_buffer = NULL; + + return ret; +} + +struct notifier_block update_buffer_nb = { + .notifier_call = ima_update_kexec_buffer, +}; + +/* + * Create a mapping for the source pages that contain the IMA buffer + * so we can update it later. + */ +void ima_kexec_post_load(struct kimage *image) +{ + if (ima_kexec_buffer) { + kimage_unmap_segment(ima_kexec_buffer); + ima_kexec_buffer = NULL; + } + + if (!image->ima_buffer_addr) + return; + + ima_kexec_buffer = kimage_map_segment(image, + image->ima_buffer_addr, + image->ima_buffer_size); + if (!ima_kexec_buffer) { + pr_err("%s: Could not map measurements buffer.\n", __func__); + return; + } + + if (!ima_kexec_update_registered) { + register_reboot_notifier(&update_buffer_nb); + ima_kexec_update_registered = true; + } +} + #endif /* IMA_KEXEC */ /*
ima_dump_measurement_list() is called during kexec 'load', which may result in loss of IMA measurements during kexec soft reboot. It needs to be called during kexec 'execute'. The below changes need to be part of the same patch to ensure this patch series remains bisect-safe by ensuring the IMA log gets copied over during kexec soft reboot both before and after this patch. Implement ima_update_kexec_buffer() to be called during kexec 'execute'. Move ima_dump_measurement_list() from ima_add_kexec_buffer() to ima_update_kexec_buffer(). Make the necessary variables local static to the file, so that they are accessible during both kexec 'load' - where the memory is allocated and mapped to a segment in the new Kernel, and during 'execute' - where the IMA log gets copied over. Implement kimage_file_post_load() and ima_kexec_post_load() to be invoked after the new Kernel image has been loaded for kexec. ima_kexec_post_load() will map the IMA buffer to a segment in the newly loaded Kernel. It will also register the reboot notifier_block to trigger ima_update_kexec_buffer() at exec 'execute'. Modify kexec_file_load() syscall to call kimage_file_post_load() after the image has been loaded and prepared for kexec. Call it only on kexec soft reboot and not for KEXEC_FILE_ON_CRASH. Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> --- include/linux/ima.h | 3 ++ kernel/kexec_file.c | 8 +++ security/integrity/ima/ima_kexec.c | 82 ++++++++++++++++++++++++++---- 3 files changed, 84 insertions(+), 9 deletions(-)