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| author | Borislav Petkov <bp@suse.de> | 2021-12-17 16:48:29 +0100 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-12-22 11:51:20 +0100 |
| commit | b64dfcde1ca9cb82e38e573753f0c0db8fb841c2 (patch) | |
| tree | 32059f1c8c20ec3a958c7a9c52ac04091fb9be5d | |
| parent | x86/mm: Include spinlock_t definition in pgtable. (diff) | |
| download | linux-b64dfcde1ca9cb82e38e573753f0c0db8fb841c2.tar.xz linux-b64dfcde1ca9cb82e38e573753f0c0db8fb841c2.zip | |
x86/mm: Prevent early boot triple-faults with instrumentation
Commit in Fixes added a global TLB flush on the early boot path, after
the kernel switches off of the trampoline page table.
Compiler profiling options enabled with GCOV_PROFILE add additional
measurement code on clang which needs to be initialized prior to
use. The global flush in x86_64_start_kernel() happens before those
initializations can happen, leading to accessing invalid memory.
GCOV_PROFILE builds with gcc are still ok so this is clang-specific.
The second issue this fixes is with KASAN: for a similar reason,
kasan_early_init() needs to have happened before KASAN-instrumented
functions are called.
Therefore, reorder the flush to happen after the KASAN early init
and prevent the compilers from adding profiling instrumentation to
native_write_cr4().
Fixes: f154f290855b ("x86/mm/64: Flush global TLB on boot and AP bringup")
Reported-by: "J. Bruce Fields" <bfields@fieldses.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Carel Si <beibei.si@intel.com>
Tested-by: "J. Bruce Fields" <bfields@fieldses.org>
Link: https://lore.kernel.org/r/20211209144141.GC25654@xsang-OptiPlex-9020
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/head64.c | 16 |
2 files changed, 15 insertions, 3 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 0083464de5e3..79b3d67addcc 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -384,7 +384,7 @@ set_register: } EXPORT_SYMBOL(native_write_cr0); -void native_write_cr4(unsigned long val) +void __no_profile native_write_cr4(unsigned long val) { unsigned long bits_changed = 0; diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 75acb6027a87..f5e80a8377ad 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -483,10 +483,12 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data) /* Kill off the identity-map trampoline */ reset_early_page_tables(); - __native_tlb_flush_global(native_read_cr4()); - clear_bss(); + /* + * This needs to happen *before* kasan_early_init() because latter maps stuff + * into that page. + */ clear_page(init_top_pgt); /* @@ -498,6 +500,16 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data) kasan_early_init(); + /* + * Flush global TLB entries which could be left over from the trampoline page + * table. + * + * This needs to happen *after* kasan_early_init() as KASAN-enabled .configs + * instrument native_write_cr4() so KASAN must be initialized for that + * instrumentation to work. + */ + __native_tlb_flush_global(this_cpu_read(cpu_tlbstate.cr4)); + idt_setup_early_handler(); copy_bootdata(__va(real_mode_data)); |