Re: [RFC PATCH 08/10] powerpc/fsl_booke/kaslr: clear the original kernel if randomized
From: Christophe Leroy <hidden>
Date: 2019-07-29 11:19:45
Also in:
linuxppc-dev
Le 17/07/2019 à 10:06, Jason Yan a écrit :
quoted hunk ↗ jump to hunk
The original kernel still exists in the memory, clear it now. Signed-off-by: Jason Yan <yanaijie@huawei.com> Cc: Diana Craciun <redacted> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Christophe Leroy <redacted> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <redacted> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Kees Cook <redacted> --- arch/powerpc/kernel/kaslr_booke.c | 11 +++++++++++ arch/powerpc/mm/mmu_decl.h | 2 ++ arch/powerpc/mm/nohash/fsl_booke.c | 1 + 3 files changed, 14 insertions(+)diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c index 90357f4bd313..00339c05879f 100644 --- a/arch/powerpc/kernel/kaslr_booke.c +++ b/arch/powerpc/kernel/kaslr_booke.c@@ -412,3 +412,14 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size) reloc_kernel_entry(dt_ptr, kimage_vaddr); } + +void __init kaslr_second_init(void) +{ + /* If randomized, clear the original kernel */ + if (kimage_vaddr != KERNELBASE) { + unsigned long kernel_sz; + + kernel_sz = (unsigned long)_end - kimage_vaddr; + memset((void *)KERNELBASE, 0, kernel_sz);
Why are we clearing ? Is that just to tidy up or is it of security importance ? If so, maybe memzero_explicit() should be used instead ?
quoted hunk ↗ jump to hunk
+ } +}diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h index 754ae1e69f92..9912ee598f9b 100644 --- a/arch/powerpc/mm/mmu_decl.h +++ b/arch/powerpc/mm/mmu_decl.h@@ -150,8 +150,10 @@ extern void loadcam_multi(int first_idx, int num, int tmp_idx); #ifdef CONFIG_RANDOMIZE_BASE extern void kaslr_early_init(void *dt_ptr, phys_addr_t size); +extern void kaslr_second_init(void);
No new 'extern' please.
quoted hunk ↗ jump to hunk
#else static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {} +static inline void kaslr_second_init(void) {} #endif struct tlbcam {diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c index 8d25a8dc965f..fa5a87f5c08e 100644 --- a/arch/powerpc/mm/nohash/fsl_booke.c +++ b/arch/powerpc/mm/nohash/fsl_booke.c@@ -269,6 +269,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start) kernstart_addr = start; if (is_second_reloc) { virt_phys_offset = PAGE_OFFSET - memstart_addr; + kaslr_second_init(); return; }
Christophe