From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 9 Jan 2015 10:09:10 +0800 From: Baoquan He To: hpa@zytor.com Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, vgoyal@redhat.com, keescook@chromium.org, ak@linux.intel.com, ebiederm@xmission.com, kexec@lists.infradead.org, whissi@whissi.de, kumagai-atsushi@mxc.nes.nec.co.jp, stable@vger.kernel.org Subject: Re: [resend Patch v3 1/2] kaslr: check if kernel location is changed Message-ID: <20150109020910.GA22338@dhcp-16-116.nay.redhat.com> References: <1412060896-1902-1-git-send-email-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412060896-1902-1-git-send-email-bhe@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Hi hpa, Ping. Do you have further plan or idea on this issue? Or could you please merge this patch to fix reported bug for now? Thanks Baoquan On 09/30/14 at 03:08pm, Baoquan He wrote: > Function handle_relocations() is used to do the relocations handling > for i686 and kaslr of x86_64. For 32 bit the relocation handling is > mandotary to perform. For x86_64 only when kaslr is enabled and a > random kernel location is chosen successfully the relocation handling > shound be done. However previous implementation only compared the > kernel loading address and LOAD_PHYSICAL_ADDR where kernel were > compiled to run at. This would casue system to be exceptional in > few conditions like when delta between load address and compiled > address is bigger than what 32bit signed relocations can handle. > Also there will be limitations that delta can't be too big otherwise > kernel text virtual addresses will overflow in module address space. > > So in this patch check if kernel location is changed after > choose_kernel_location() when x86_64. If and only if in x86_64 > and kernel location is changed, we say a kaslr random kernel > location is chosen, then the relocation handling is needed. > > Signed-off-by: Baoquan He > Acked-by: Vivek Goyal > Acked-by: Kees Cook > Tested-by: Thomas D. > Cc: stable@vger.kernel.org > --- > arch/x86/boot/compressed/misc.c | 26 ++++++++++++++++++++++---- > 1 file changed, 22 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c > index 57ab74d..3bb2a17 100644 > --- a/arch/x86/boot/compressed/misc.c > +++ b/arch/x86/boot/compressed/misc.c > @@ -230,8 +230,9 @@ static void error(char *x) > asm("hlt"); > } > > -#if CONFIG_X86_NEED_RELOCS > -static void handle_relocations(void *output, unsigned long output_len) > +#ifdef CONFIG_X86_NEED_RELOCS > +static void handle_relocations(void *output_orig, void *output, > + unsigned long output_len) > { > int *reloc; > unsigned long delta, map, ptr; > @@ -239,6 +240,20 @@ static void handle_relocations(void *output, unsigned long output_len) > unsigned long max_addr = min_addr + output_len; > > /* > + * 32bit always requires relocations to be performed. For x86_64, > + * relocations need to be performed only if kaslr has chosen a > + * different load address then kernel was originally loaded at. > + * > + * If we are here, either kaslr is not configured in or kaslr is disabled > + * or kaslr has chosen not to change the load location of kernel. Don't > + * perform any relocations. > + */ > +#if CONFIG_X86_64 > + if (output_orig == output) > + return; > +#endif > + > + /* > * Calculate the delta between where vmlinux was linked to load > * and where it was actually loaded. > */ > @@ -299,7 +314,8 @@ static void handle_relocations(void *output, unsigned long output_len) > #endif > } > #else > -static inline void handle_relocations(void *output, unsigned long output_len) > +static inline void handle_relocations(void *output_orig, void *output, > + unsigned long output_len) > { } > #endif > > @@ -360,6 +376,8 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, > unsigned char *output, > unsigned long output_len) > { > + unsigned char *output_orig = output; > + > real_mode = rmode; > > sanitize_boot_params(real_mode); > @@ -402,7 +420,7 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, > debug_putstr("\nDecompressing Linux... "); > decompress(input_data, input_len, NULL, NULL, output, NULL, error); > parse_elf(output); > - handle_relocations(output, output_len); > + handle_relocations(output_orig, output, output_len); > debug_putstr("done.\nBooting the kernel.\n"); > return output; > } > -- > 1.8.5.3 >