From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: Re: [PATCH] efi/libstub: arm/arm64: don't use TASK_SIZE when randomising the RT space Date: Mon, 10 Apr 2017 11:44:03 +0100 Message-ID: <20170410104403.GC13899@leverpostej> References: <20170410103038.20117-1-ard.biesheuvel@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170410103038.20117-1-ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ard Biesheuvel Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, James Morse , Catalin Marinas , Matt Fleming , Ingo Molnar List-Id: linux-efi@vger.kernel.org On Mon, Apr 10, 2017 at 11:30:38AM +0100, Ard Biesheuvel wrote: > As reported by James, Catalin and Mark, commit e69176d68d26 > ("ef/libstub/arm/arm64: Randomize the base of the UEFI rt services > region") results in a crash in the firmware regardless of whether KASLR > is in effect or not, and whether the firmware implements EFI_RNG_PROTOCOL > or not. > > Mark has identified the root cause to be the inappropriate use of > TASK_SIZE in the stub, which arm64 defines as > > #define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \ > TASK_SIZE_32 : TASK_SIZE_64) > > and testing thread flags at this point results in the dereference of > pointers in uninitialized structures. > > So instead, introduce a preprocessor symbol EFI_RT_VIRTUAL_LIMIT and > define it to TASK_SIZE_64 on arm64 and TASK_SIZE on ARM, both of which > are compile time constants. Also, change the 'headroom' variable to > static const to force an error if this changes in the future. > > Cc: James Morse > Cc: Mark Rutland > Cc: Catalin Marinas > Cc: Matt Fleming > Cc: Ingo Molnar > Signed-off-by: Ard Biesheuvel With this patch applied atop of next-20170410, a defconfig arm64 kernel built with the Linaro 15.08 toolchain boots happily for me on Juno R1. So FWIW: Tested-by: Mark Rutland Thanks, Mark. > --- > > Apologies for the breakage. On the systems I have tested, sp_el0 apparently > pointed somewhere sane when I inadvertently dereferenced it, and the > resulting addresses looked sufficiently random to me. > > Ingo, once we have some confirmation that this makes the problem go away, > could you please take this straight into efi/core? Thanks. > > drivers/firmware/efi/libstub/arm-stub.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c > index 1e45ec51b094..34010ff3b77e 100644 > --- a/drivers/firmware/efi/libstub/arm-stub.c > +++ b/drivers/firmware/efi/libstub/arm-stub.c > @@ -32,6 +32,12 @@ > #define EFI_RT_VIRTUAL_BASE SZ_512M > #define EFI_RT_VIRTUAL_SIZE SZ_512M > > +#ifdef CONFIG_ARM64 > +#define EFI_RT_VIRTUAL_LIMIT TASK_SIZE_64 > +#else > +#define EFI_RT_VIRTUAL_LIMIT TASK_SIZE > +#endif > + > static u64 virtmap_base = EFI_RT_VIRTUAL_BASE; > > efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, > @@ -236,8 +242,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, > * shift of 21 bit positions into account when scaling > * the headroom value using a 32-bit random value. > */ > - u64 headroom = TASK_SIZE - EFI_RT_VIRTUAL_BASE - > - EFI_RT_VIRTUAL_SIZE; > + static const u64 headroom = EFI_RT_VIRTUAL_LIMIT - > + EFI_RT_VIRTUAL_BASE - > + EFI_RT_VIRTUAL_SIZE; > u32 rnd; > > status = efi_get_random_bytes(sys_table, sizeof(rnd), > -- > 2.9.3 > From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Mon, 10 Apr 2017 11:44:03 +0100 Subject: [PATCH] efi/libstub: arm/arm64: don't use TASK_SIZE when randomising the RT space In-Reply-To: <20170410103038.20117-1-ard.biesheuvel@linaro.org> References: <20170410103038.20117-1-ard.biesheuvel@linaro.org> Message-ID: <20170410104403.GC13899@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Apr 10, 2017 at 11:30:38AM +0100, Ard Biesheuvel wrote: > As reported by James, Catalin and Mark, commit e69176d68d26 > ("ef/libstub/arm/arm64: Randomize the base of the UEFI rt services > region") results in a crash in the firmware regardless of whether KASLR > is in effect or not, and whether the firmware implements EFI_RNG_PROTOCOL > or not. > > Mark has identified the root cause to be the inappropriate use of > TASK_SIZE in the stub, which arm64 defines as > > #define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \ > TASK_SIZE_32 : TASK_SIZE_64) > > and testing thread flags at this point results in the dereference of > pointers in uninitialized structures. > > So instead, introduce a preprocessor symbol EFI_RT_VIRTUAL_LIMIT and > define it to TASK_SIZE_64 on arm64 and TASK_SIZE on ARM, both of which > are compile time constants. Also, change the 'headroom' variable to > static const to force an error if this changes in the future. > > Cc: James Morse > Cc: Mark Rutland > Cc: Catalin Marinas > Cc: Matt Fleming > Cc: Ingo Molnar > Signed-off-by: Ard Biesheuvel With this patch applied atop of next-20170410, a defconfig arm64 kernel built with the Linaro 15.08 toolchain boots happily for me on Juno R1. So FWIW: Tested-by: Mark Rutland Thanks, Mark. > --- > > Apologies for the breakage. On the systems I have tested, sp_el0 apparently > pointed somewhere sane when I inadvertently dereferenced it, and the > resulting addresses looked sufficiently random to me. > > Ingo, once we have some confirmation that this makes the problem go away, > could you please take this straight into efi/core? Thanks. > > drivers/firmware/efi/libstub/arm-stub.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c > index 1e45ec51b094..34010ff3b77e 100644 > --- a/drivers/firmware/efi/libstub/arm-stub.c > +++ b/drivers/firmware/efi/libstub/arm-stub.c > @@ -32,6 +32,12 @@ > #define EFI_RT_VIRTUAL_BASE SZ_512M > #define EFI_RT_VIRTUAL_SIZE SZ_512M > > +#ifdef CONFIG_ARM64 > +#define EFI_RT_VIRTUAL_LIMIT TASK_SIZE_64 > +#else > +#define EFI_RT_VIRTUAL_LIMIT TASK_SIZE > +#endif > + > static u64 virtmap_base = EFI_RT_VIRTUAL_BASE; > > efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, > @@ -236,8 +242,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, > * shift of 21 bit positions into account when scaling > * the headroom value using a 32-bit random value. > */ > - u64 headroom = TASK_SIZE - EFI_RT_VIRTUAL_BASE - > - EFI_RT_VIRTUAL_SIZE; > + static const u64 headroom = EFI_RT_VIRTUAL_LIMIT - > + EFI_RT_VIRTUAL_BASE - > + EFI_RT_VIRTUAL_SIZE; > u32 rnd; > > status = efi_get_random_bytes(sys_table, sizeof(rnd), > -- > 2.9.3 >