| Message ID | 55f8561f1ee207237fdcfbc8c5dc043be06d3de6.1567077734.git.viresh.kumar@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | V4.4 backport of arm64 Spectre patches | expand |
On Thu, Aug 29, 2019 at 05:03:49PM +0530, Viresh Kumar wrote: > From: Robin Murphy <robin.murphy@arm.com> > > commit 51369e398d0d33e8f524314e672b07e8cf870e79 upstream. > > Currently, USER_DS represents an exclusive limit while KERNEL_DS is > inclusive. In order to do some clever trickery for speculation-safe > masking, we need them both to behave equivalently - there aren't enough > bits to make KERNEL_DS exclusive, so we have precisely one option. This > also happens to correct a longstanding false negative for a range > ending on the very top byte of kernel memory. > > Mark Rutland points out that we've actually got the semantics of > addresses vs. segments muddled up in most of the places we need to > amend, so shuffle the {USER,KERNEL}_DS definitions around such that we > can correct those properly instead of just pasting "-1"s everywhere. > > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > Signed-off-by: Will Deacon <will.deacon@arm.com> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > [ 4.4: Dropped changes from fault.c and fixed minor rebase conflict ] > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> [v4.4 backport] Mark. > --- > arch/arm64/include/asm/processor.h | 3 ++ > arch/arm64/include/asm/uaccess.h | 45 +++++++++++++++++------------- > arch/arm64/kernel/entry.S | 4 +-- > 3 files changed, 31 insertions(+), 21 deletions(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index 75d9ef6c457c..ff1449c25bf4 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -21,6 +21,9 @@ > > #define TASK_SIZE_64 (UL(1) << VA_BITS) > > +#define KERNEL_DS UL(-1) > +#define USER_DS (TASK_SIZE_64 - 1) > + > #ifndef __ASSEMBLY__ > > /* > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > index 829fa6d3e561..c625cc5531fc 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -56,10 +56,7 @@ struct exception_table_entry > > extern int fixup_exception(struct pt_regs *regs); > > -#define KERNEL_DS (-1UL) > #define get_ds() (KERNEL_DS) > - > -#define USER_DS TASK_SIZE_64 > #define get_fs() (current_thread_info()->addr_limit) > > static inline void set_fs(mm_segment_t fs) > @@ -87,22 +84,32 @@ static inline void set_fs(mm_segment_t fs) > * Returns 1 if the range is valid, 0 otherwise. > * > * This is equivalent to the following test: > - * (u65)addr + (u65)size <= current->addr_limit > - * > - * This needs 65-bit arithmetic. > + * (u65)addr + (u65)size <= (u65)current->addr_limit + 1 > */ > -#define __range_ok(addr, size) \ > -({ \ > - unsigned long __addr = (unsigned long __force)(addr); \ > - unsigned long flag, roksum; \ > - __chk_user_ptr(addr); \ > - asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls" \ > - : "=&r" (flag), "=&r" (roksum) \ > - : "1" (__addr), "Ir" (size), \ > - "r" (current_thread_info()->addr_limit) \ > - : "cc"); \ > - flag; \ > -}) > +static inline unsigned long __range_ok(unsigned long addr, unsigned long size) > +{ > + unsigned long limit = current_thread_info()->addr_limit; > + > + __chk_user_ptr(addr); > + asm volatile( > + // A + B <= C + 1 for all A,B,C, in four easy steps: > + // 1: X = A + B; X' = X % 2^64 > + " adds %0, %0, %2\n" > + // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4 > + " csel %1, xzr, %1, hi\n" > + // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X' > + // to compensate for the carry flag being set in step 4. For > + // X > 2^64, X' merely has to remain nonzero, which it does. > + " csinv %0, %0, xzr, cc\n" > + // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1 > + // comes from the carry in being clear. Otherwise, we are > + // testing X' - C == 0, subject to the previous adjustments. > + " sbcs xzr, %0, %1\n" > + " cset %0, ls\n" > + : "+r" (addr), "+r" (limit) : "Ir" (size) : "cc"); > + > + return addr; > +} > > /* > * When dealing with data aborts, watchpoints, or instruction traps we may end > @@ -111,7 +118,7 @@ static inline void set_fs(mm_segment_t fs) > */ > #define untagged_addr(addr) sign_extend64(addr, 55) > > -#define access_ok(type, addr, size) __range_ok(addr, size) > +#define access_ok(type, addr, size) __range_ok((unsigned long)(addr), size) > #define user_addr_max get_fs > > /* > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index c849be9231bb..4c5013b09dcb 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -96,10 +96,10 @@ > .else > add x21, sp, #S_FRAME_SIZE > get_thread_info tsk > - /* Save the task's original addr_limit and set USER_DS (TASK_SIZE_64) */ > + /* Save the task's original addr_limit and set USER_DS */ > ldr x20, [tsk, #TI_ADDR_LIMIT] > str x20, [sp, #S_ORIG_ADDR_LIMIT] > - mov x20, #TASK_SIZE_64 > + mov x20, #USER_DS > str x20, [tsk, #TI_ADDR_LIMIT] > .endif /* \el == 0 */ > mrs x22, elr_el1 > -- > 2.21.0.rc0.269.g1a574e7a288b >
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 75d9ef6c457c..ff1449c25bf4 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -21,6 +21,9 @@ #define TASK_SIZE_64 (UL(1) << VA_BITS) +#define KERNEL_DS UL(-1) +#define USER_DS (TASK_SIZE_64 - 1) + #ifndef __ASSEMBLY__ /* diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 829fa6d3e561..c625cc5531fc 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -56,10 +56,7 @@ struct exception_table_entry extern int fixup_exception(struct pt_regs *regs); -#define KERNEL_DS (-1UL) #define get_ds() (KERNEL_DS) - -#define USER_DS TASK_SIZE_64 #define get_fs() (current_thread_info()->addr_limit) static inline void set_fs(mm_segment_t fs) @@ -87,22 +84,32 @@ static inline void set_fs(mm_segment_t fs) * Returns 1 if the range is valid, 0 otherwise. * * This is equivalent to the following test: - * (u65)addr + (u65)size <= current->addr_limit - * - * This needs 65-bit arithmetic. + * (u65)addr + (u65)size <= (u65)current->addr_limit + 1 */ -#define __range_ok(addr, size) \ -({ \ - unsigned long __addr = (unsigned long __force)(addr); \ - unsigned long flag, roksum; \ - __chk_user_ptr(addr); \ - asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls" \ - : "=&r" (flag), "=&r" (roksum) \ - : "1" (__addr), "Ir" (size), \ - "r" (current_thread_info()->addr_limit) \ - : "cc"); \ - flag; \ -}) +static inline unsigned long __range_ok(unsigned long addr, unsigned long size) +{ + unsigned long limit = current_thread_info()->addr_limit; + + __chk_user_ptr(addr); + asm volatile( + // A + B <= C + 1 for all A,B,C, in four easy steps: + // 1: X = A + B; X' = X % 2^64 + " adds %0, %0, %2\n" + // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4 + " csel %1, xzr, %1, hi\n" + // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X' + // to compensate for the carry flag being set in step 4. For + // X > 2^64, X' merely has to remain nonzero, which it does. + " csinv %0, %0, xzr, cc\n" + // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1 + // comes from the carry in being clear. Otherwise, we are + // testing X' - C == 0, subject to the previous adjustments. + " sbcs xzr, %0, %1\n" + " cset %0, ls\n" + : "+r" (addr), "+r" (limit) : "Ir" (size) : "cc"); + + return addr; +} /* * When dealing with data aborts, watchpoints, or instruction traps we may end @@ -111,7 +118,7 @@ static inline void set_fs(mm_segment_t fs) */ #define untagged_addr(addr) sign_extend64(addr, 55) -#define access_ok(type, addr, size) __range_ok(addr, size) +#define access_ok(type, addr, size) __range_ok((unsigned long)(addr), size) #define user_addr_max get_fs /* diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index c849be9231bb..4c5013b09dcb 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -96,10 +96,10 @@ .else add x21, sp, #S_FRAME_SIZE get_thread_info tsk - /* Save the task's original addr_limit and set USER_DS (TASK_SIZE_64) */ + /* Save the task's original addr_limit and set USER_DS */ ldr x20, [tsk, #TI_ADDR_LIMIT] str x20, [sp, #S_ORIG_ADDR_LIMIT] - mov x20, #TASK_SIZE_64 + mov x20, #USER_DS str x20, [tsk, #TI_ADDR_LIMIT] .endif /* \el == 0 */ mrs x22, elr_el1