When the second-stage kernel is booted with a limiting command line (e.g. "mem=<size>"), the IMA measurement buffer handed over from the previous kernel may fall outside the addressable RAM of the new kernel. Accessing such a buffer can fault during early restore.
Introduce a small generic helper, ima_validate_range(), which verifies that a physical [start, end] range for the previous-kernel IMA buffer lies within addressable memory: - On x86, use pfn_range_is_mapped(). - On OF based architectures, use page_is_ram().
Cc: stable@vger.kernel.org Signed-off-by: Harshit Mogalapalli harshit.m.mogalapalli@oracle.com --- v2->v3: Update subject to exactly describe the patch [ Suggested by Mimi Zohar] --- include/linux/ima.h | 1 + security/integrity/ima/ima_kexec.c | 35 ++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+)
diff --git a/include/linux/ima.h b/include/linux/ima.h index 8e29cb4e6a01..abf8923f8fc5 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -69,6 +69,7 @@ static inline int ima_measure_critical_data(const char *event_label, #ifdef CONFIG_HAVE_IMA_KEXEC int __init ima_free_kexec_buffer(void); int __init ima_get_kexec_buffer(void **addr, size_t *size); +int ima_validate_range(phys_addr_t phys, size_t size); #endif
#ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c index 7362f68f2d8b..8b24e3312ea0 100644 --- a/security/integrity/ima/ima_kexec.c +++ b/security/integrity/ima/ima_kexec.c @@ -12,6 +12,8 @@ #include <linux/kexec.h> #include <linux/of.h> #include <linux/ima.h> +#include <linux/mm.h> +#include <linux/overflow.h> #include <linux/reboot.h> #include <asm/page.h> #include "ima.h" @@ -296,3 +298,36 @@ void __init ima_load_kexec_buffer(void) pr_debug("Error restoring the measurement list: %d\n", rc); } } + +/* + * ima_validate_range - verify a physical buffer lies in addressable RAM + * @phys: physical start address of the buffer from previous kernel + * @size: size of the buffer + * + * On success return 0. On failure returns -EINVAL so callers can skip + * restoring. + */ +int ima_validate_range(phys_addr_t phys, size_t size) +{ + unsigned long start_pfn, end_pfn; + phys_addr_t end_phys; + + if (check_add_overflow(phys, (phys_addr_t)size - 1, &end_phys)) + return -EINVAL; + + start_pfn = PHYS_PFN(phys); + end_pfn = PHYS_PFN(end_phys); + +#ifdef CONFIG_X86 + if (!pfn_range_is_mapped(start_pfn, end_pfn)) +#else + if (!page_is_ram(start_pfn) || !page_is_ram(end_pfn)) +#endif + { + pr_warn("IMA: previous kernel measurement buffer %pa (size 0x%zx) lies outside available memory\n", + &phys, size); + return -EINVAL; + } + + return 0; +}