diff options
Diffstat (limited to 'arch/x86/mm/init.c')
| -rw-r--r-- | arch/x86/mm/init.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index bc11dedffc45..74b157ac078d 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -780,8 +780,30 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end) */ void free_kernel_image_pages(void *begin, void *end) { - free_init_pages("unused kernel image", - (unsigned long)begin, (unsigned long)end); + unsigned long begin_ul = (unsigned long)begin; + unsigned long end_ul = (unsigned long)end; + unsigned long len_pages = (end_ul - begin_ul) >> PAGE_SHIFT; + + + free_init_pages("unused kernel image", begin_ul, end_ul); + + /* + * PTI maps some of the kernel into userspace. For performance, + * this includes some kernel areas that do not contain secrets. + * Those areas might be adjacent to the parts of the kernel image + * being freed, which may contain secrets. Remove the "high kernel + * image mapping" for these freed areas, ensuring they are not even + * potentially vulnerable to Meltdown regardless of the specific + * optimizations PTI is currently using. + * + * The "noalias" prevents unmapping the direct map alias which is + * needed to access the freed pages. + * + * This is only valid for 64bit kernels. 32bit has only one mapping + * which can't be treated in this way for obvious reasons. + */ + if (IS_ENABLED(CONFIG_X86_64) && cpu_feature_enabled(X86_FEATURE_PTI)) + set_memory_np_noalias(begin_ul, len_pages); } void __ref free_initmem(void) |