Messages in this thread | | | Subject | Re: [RFC PATCH 08/10] powerpc/fsl_booke/kaslr: clear the original kernel if randomized | From | Christophe Leroy <> | Date | Mon, 29 Jul 2019 13:19:41 +0200 |
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Le 17/07/2019 à 10:06, Jason Yan a écrit : > The original kernel still exists in the memory, clear it now. > > Signed-off-by: Jason Yan <yanaijie@huawei.com> > Cc: Diana Craciun <diana.craciun@nxp.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Christophe Leroy <christophe.leroy@c-s.fr> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: Kees Cook <keescook@chromium.org> > --- > 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 ?
> + } > +} > 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.
> #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
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