diff options
| -rw-r--r-- | arch/x86/include/asm/fpu/api.h | 4 | ||||
| -rw-r--r-- | arch/x86/include/asm/proto.h | 2 | ||||
| -rw-r--r-- | arch/x86/include/uapi/asm/prctl.h | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 156 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.h | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 9 |
6 files changed, 178 insertions, 3 deletions
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index e9379d7e7743..798ae9225f0e 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -151,4 +151,8 @@ static inline bool fpstate_is_confidential(struct fpu_guest *gfpu) return gfpu->fpstate->is_confidential; } +/* prctl */ +struct task_struct; +extern long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2); + #endif /* _ASM_X86_FPU_API_H */ diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h index 8c5d1910a848..feed36d44d04 100644 --- a/arch/x86/include/asm/proto.h +++ b/arch/x86/include/asm/proto.h @@ -40,6 +40,6 @@ void x86_report_nx(void); extern int reboot_force; long do_arch_prctl_common(struct task_struct *task, int option, - unsigned long cpuid_enabled); + unsigned long arg2); #endif /* _ASM_X86_PROTO_H */ diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 5a6aac9fa41f..754a07856817 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -10,6 +10,10 @@ #define ARCH_GET_CPUID 0x1011 #define ARCH_SET_CPUID 0x1012 +#define ARCH_GET_XCOMP_SUPP 0x1021 +#define ARCH_GET_XCOMP_PERM 0x1022 +#define ARCH_REQ_XCOMP_PERM 0x1023 + #define ARCH_MAP_VDSO_X32 0x2001 #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 310c4201e056..c837cffebd4a 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -8,6 +8,7 @@ #include <linux/compat.h> #include <linux/cpu.h> #include <linux/mman.h> +#include <linux/nospec.h> #include <linux/pkeys.h> #include <linux/seq_file.h> #include <linux/proc_fs.h> @@ -18,6 +19,8 @@ #include <asm/fpu/xcr.h> #include <asm/tlbflush.h> +#include <asm/prctl.h> +#include <asm/elf.h> #include "internal.h" #include "legacy.h" @@ -1298,6 +1301,159 @@ void fpstate_clear_xstate_component(struct fpstate *fps, unsigned int xfeature) EXPORT_SYMBOL_GPL(fpstate_clear_xstate_component); #endif +#ifdef CONFIG_X86_64 +static int validate_sigaltstack(unsigned int usize) +{ + struct task_struct *thread, *leader = current->group_leader; + unsigned long framesize = get_sigframe_size(); + + lockdep_assert_held(¤t->sighand->siglock); + + /* get_sigframe_size() is based on fpu_user_cfg.max_size */ + framesize -= fpu_user_cfg.max_size; + framesize += usize; + for_each_thread(leader, thread) { + if (thread->sas_ss_size && thread->sas_ss_size < framesize) + return -ENOSPC; + } + return 0; +} + +static int __xstate_request_perm(u64 permitted, u64 requested) +{ + /* + * This deliberately does not exclude !XSAVES as we still might + * decide to optionally context switch XCR0 or talk the silicon + * vendors into extending XFD for the pre AMX states. + */ + bool compacted = cpu_feature_enabled(X86_FEATURE_XSAVES); + struct fpu *fpu = ¤t->group_leader->thread.fpu; + unsigned int ksize, usize; + u64 mask; + int ret; + + /* Check whether fully enabled */ + if ((permitted & requested) == requested) + return 0; + + /* Calculate the resulting kernel state size */ + mask = permitted | requested; + ksize = xstate_calculate_size(mask, compacted); + + /* Calculate the resulting user state size */ + mask &= XFEATURE_MASK_USER_SUPPORTED; + usize = xstate_calculate_size(mask, false); + + ret = validate_sigaltstack(usize); + if (ret) + return ret; + + /* Pairs with the READ_ONCE() in xstate_get_group_perm() */ + WRITE_ONCE(fpu->perm.__state_perm, requested); + /* Protected by sighand lock */ + fpu->perm.__state_size = ksize; + fpu->perm.__user_state_size = usize; + return ret; +} + +/* + * Permissions array to map facilities with more than one component + */ +static const u64 xstate_prctl_req[XFEATURE_MAX] = { + /* [XFEATURE_XTILE_DATA] = XFEATURE_MASK_XTILE, */ +}; + +static int xstate_request_perm(unsigned long idx) +{ + u64 permitted, requested; + int ret; + + if (idx >= XFEATURE_MAX) + return -EINVAL; + + /* + * Look up the facility mask which can require more than + * one xstate component. + */ + idx = array_index_nospec(idx, ARRAY_SIZE(xstate_prctl_req)); + requested = xstate_prctl_req[idx]; + if (!requested) + return -EOPNOTSUPP; + + if ((fpu_user_cfg.max_features & requested) != requested) + return -EOPNOTSUPP; + + /* Lockless quick check */ + permitted = xstate_get_host_group_perm(); + if ((permitted & requested) == requested) + return 0; + + /* Protect against concurrent modifications */ + spin_lock_irq(¤t->sighand->siglock); + permitted = xstate_get_host_group_perm(); + ret = __xstate_request_perm(permitted, requested); + spin_unlock_irq(¤t->sighand->siglock); + return ret; +} +#else /* CONFIG_X86_64 */ +static inline int xstate_request_perm(unsigned long idx) +{ + return -EPERM; +} +#endif /* !CONFIG_X86_64 */ + +/** + * fpu_xstate_prctl - xstate permission operations + * @tsk: Redundant pointer to current + * @option: A subfunction of arch_prctl() + * @arg2: option argument + * Return: 0 if successful; otherwise, an error code + * + * Option arguments: + * + * ARCH_GET_XCOMP_SUPP: Pointer to user space u64 to store the info + * ARCH_GET_XCOMP_PERM: Pointer to user space u64 to store the info + * ARCH_REQ_XCOMP_PERM: Facility number requested + * + * For facilities which require more than one XSTATE component, the request + * must be the highest state component number related to that facility, + * e.g. for AMX which requires XFEATURE_XTILE_CFG(17) and + * XFEATURE_XTILE_DATA(18) this would be XFEATURE_XTILE_DATA(18). + */ +long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2) +{ + u64 __user *uptr = (u64 __user *)arg2; + u64 permitted, supported; + unsigned long idx = arg2; + + if (tsk != current) + return -EPERM; + + switch (option) { + case ARCH_GET_XCOMP_SUPP: + supported = fpu_user_cfg.max_features | fpu_user_cfg.legacy_features; + return put_user(supported, uptr); + + case ARCH_GET_XCOMP_PERM: + /* + * Lockless snapshot as it can also change right after the + * dropping the lock. + */ + permitted = xstate_get_host_group_perm(); + permitted &= XFEATURE_MASK_USER_SUPPORTED; + return put_user(permitted, uptr); + + case ARCH_REQ_XCOMP_PERM: + if (!IS_ENABLED(CONFIG_X86_64)) + return -EOPNOTSUPP; + + return xstate_request_perm(idx); + + default: + return -EINVAL; + } +} + #ifdef CONFIG_PROC_PID_ARCH_STATUS /* * Report the amount of time elapsed in millisecond since last AVX512 diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h index a1aa0bad2c9c..4ce1dc030f38 100644 --- a/arch/x86/kernel/fpu/xstate.h +++ b/arch/x86/kernel/fpu/xstate.h @@ -15,6 +15,12 @@ static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask) xsave->header.xcomp_bv = mask | XCOMP_BV_COMPACTED_FORMAT; } +static inline u64 xstate_get_host_group_perm(void) +{ + /* Pairs with WRITE_ONCE() in xstate_request_perm() */ + return READ_ONCE(current->group_leader->thread.fpu.perm.__state_perm); +} + enum xstate_copy_mode { XSTATE_COPY_FP, XSTATE_COPY_FX, diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index c74c7e889e9d..97fea1649a5e 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -30,6 +30,7 @@ #include <asm/apic.h> #include <linux/uaccess.h> #include <asm/mwait.h> +#include <asm/fpu/api.h> #include <asm/fpu/sched.h> #include <asm/debugreg.h> #include <asm/nmi.h> @@ -1003,13 +1004,17 @@ out: } long do_arch_prctl_common(struct task_struct *task, int option, - unsigned long cpuid_enabled) + unsigned long arg2) { switch (option) { case ARCH_GET_CPUID: return get_cpuid_mode(); case ARCH_SET_CPUID: - return set_cpuid_mode(task, cpuid_enabled); + return set_cpuid_mode(task, arg2); + case ARCH_GET_XCOMP_SUPP: + case ARCH_GET_XCOMP_PERM: + case ARCH_REQ_XCOMP_PERM: + return fpu_xstate_prctl(task, option, arg2); } return -EINVAL; |