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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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0abdeff598
When refactoring the sigreturn code to handle SVE, I changed the sigreturn implementation to store the new FPSIMD state from the user sigframe into task_struct before reloading the state into the CPU regs. This makes it easier to convert the data for SVE when needed. However, it turns out that the fpsimd_state structure passed into fpsimd_update_current_state is not fully initialised, so assigning the structure as a whole corrupts current->thread.fpsimd_state.cpu with uninitialised data. This means that if the garbage data written to .cpu happens to be a valid cpu number, and the task is subsequently migrated to the cpu identified by the that number, and then tries to enter userspace, the CPU FPSIMD regs will be assumed to be correct for the task and not reloaded as they should be. This can result in returning to userspace with the FPSIMD registers containing data that is stale or that belongs to another task or to the kernel. Knowingly handing around a kernel structure that is incompletely initialised with user data is a potential source of mistakes, especially across source file boundaries. To help avoid a repeat of this issue, this patch adapts the relevant internal API to hand around the user-accessible subset only: struct user_fpsimd_state. To avoid future surprises, this patch also converts all uses of struct fpsimd_state that really only access the user subset, to use struct user_fpsimd_state. A few missing consts are added to function prototypes for good measure. Thanks to Will for spotting the cause of the bug here. Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Dave Martin <Dave.Martin@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
146 lines
4.1 KiB
C
146 lines
4.1 KiB
C
/*
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* Copyright (C) 2012 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __ASM_FP_H
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#define __ASM_FP_H
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#include <asm/ptrace.h>
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#include <asm/errno.h>
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#ifndef __ASSEMBLY__
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#include <linux/cache.h>
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#include <linux/stddef.h>
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/*
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* FP/SIMD storage area has:
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* - FPSR and FPCR
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* - 32 128-bit data registers
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*
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* Note that user_fpsimd forms a prefix of this structure, which is
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* relied upon in the ptrace FP/SIMD accessors.
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*/
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struct fpsimd_state {
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union {
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struct user_fpsimd_state user_fpsimd;
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struct {
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__uint128_t vregs[32];
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u32 fpsr;
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u32 fpcr;
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/*
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* For ptrace compatibility, pad to next 128-bit
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* boundary here if extending this struct.
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*/
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};
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};
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/* the id of the last cpu to have restored this state */
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unsigned int cpu;
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};
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#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
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/* Masks for extracting the FPSR and FPCR from the FPSCR */
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#define VFP_FPSCR_STAT_MASK 0xf800009f
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#define VFP_FPSCR_CTRL_MASK 0x07f79f00
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/*
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* The VFP state has 32x64-bit registers and a single 32-bit
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* control/status register.
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*/
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#define VFP_STATE_SIZE ((32 * 8) + 4)
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#endif
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struct task_struct;
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extern void fpsimd_save_state(struct fpsimd_state *state);
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extern void fpsimd_load_state(struct fpsimd_state *state);
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extern void fpsimd_thread_switch(struct task_struct *next);
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extern void fpsimd_flush_thread(void);
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extern void fpsimd_signal_preserve_current_state(void);
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extern void fpsimd_preserve_current_state(void);
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extern void fpsimd_restore_current_state(void);
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extern void fpsimd_update_current_state(struct user_fpsimd_state const *state);
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extern void fpsimd_flush_task_state(struct task_struct *target);
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extern void sve_flush_cpu_state(void);
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/* Maximum VL that SVE VL-agnostic software can transparently support */
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#define SVE_VL_ARCH_MAX 0x100
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extern void sve_save_state(void *state, u32 *pfpsr);
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extern void sve_load_state(void const *state, u32 const *pfpsr,
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unsigned long vq_minus_1);
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extern unsigned int sve_get_vl(void);
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extern int sve_kernel_enable(void *);
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extern int __ro_after_init sve_max_vl;
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#ifdef CONFIG_ARM64_SVE
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extern size_t sve_state_size(struct task_struct const *task);
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extern void sve_alloc(struct task_struct *task);
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extern void fpsimd_release_task(struct task_struct *task);
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extern void fpsimd_sync_to_sve(struct task_struct *task);
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extern void sve_sync_to_fpsimd(struct task_struct *task);
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extern void sve_sync_from_fpsimd_zeropad(struct task_struct *task);
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extern int sve_set_vector_length(struct task_struct *task,
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unsigned long vl, unsigned long flags);
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extern int sve_set_current_vl(unsigned long arg);
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extern int sve_get_current_vl(void);
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/*
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* Probing and setup functions.
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* Calls to these functions must be serialised with one another.
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*/
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extern void __init sve_init_vq_map(void);
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extern void sve_update_vq_map(void);
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extern int sve_verify_vq_map(void);
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extern void __init sve_setup(void);
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#else /* ! CONFIG_ARM64_SVE */
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static inline void sve_alloc(struct task_struct *task) { }
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static inline void fpsimd_release_task(struct task_struct *task) { }
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static inline void sve_sync_to_fpsimd(struct task_struct *task) { }
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static inline void sve_sync_from_fpsimd_zeropad(struct task_struct *task) { }
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static inline int sve_set_current_vl(unsigned long arg)
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{
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return -EINVAL;
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}
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static inline int sve_get_current_vl(void)
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{
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return -EINVAL;
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}
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static inline void sve_init_vq_map(void) { }
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static inline void sve_update_vq_map(void) { }
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static inline int sve_verify_vq_map(void) { return 0; }
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static inline void sve_setup(void) { }
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#endif /* ! CONFIG_ARM64_SVE */
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/* For use by EFI runtime services calls only */
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extern void __efi_fpsimd_begin(void);
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extern void __efi_fpsimd_end(void);
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#endif
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#endif
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