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ce0ee4e6ac
Today the sh code allocates memory the first time a process uses
the fpu. If that memory allocation fails, kill the affected task
with force_sig(SIGKILL) rather than do_group_exit(SIGKILL).
Calling do_group_exit from an exception handler can potentially lead
to dead locks as do_group_exit is not designed to be called from
interrupt context. Instead use force_sig(SIGKILL) to kill the
userspace process. Sending signals in general and force_sig in
particular has been tested from interrupt context so there should be
no problems.
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Fixes: 0ea820cf9b ("sh: Move over to dynamically allocated FPU context.")
Link: https://lkml.kernel.org/r/20211020174406.17889-6-ebiederm@xmission.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
92 lines
1.8 KiB
C
92 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/sched/signal.h>
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#include <linux/sched/task.h>
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#include <linux/sched/task_stack.h>
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#include <linux/slab.h>
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#include <asm/processor.h>
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#include <asm/fpu.h>
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#include <asm/traps.h>
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#include <asm/ptrace.h>
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int init_fpu(struct task_struct *tsk)
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{
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if (tsk_used_math(tsk)) {
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if ((boot_cpu_data.flags & CPU_HAS_FPU) && tsk == current)
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unlazy_fpu(tsk, task_pt_regs(tsk));
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return 0;
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}
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/*
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* Memory allocation at the first usage of the FPU and other state.
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*/
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if (!tsk->thread.xstate) {
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tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
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GFP_KERNEL);
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if (!tsk->thread.xstate)
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return -ENOMEM;
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}
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if (boot_cpu_data.flags & CPU_HAS_FPU) {
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struct sh_fpu_hard_struct *fp = &tsk->thread.xstate->hardfpu;
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memset(fp, 0, xstate_size);
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fp->fpscr = FPSCR_INIT;
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} else {
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struct sh_fpu_soft_struct *fp = &tsk->thread.xstate->softfpu;
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memset(fp, 0, xstate_size);
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fp->fpscr = FPSCR_INIT;
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}
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set_stopped_child_used_math(tsk);
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return 0;
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}
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#ifdef CONFIG_SH_FPU
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void __fpu_state_restore(void)
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{
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struct task_struct *tsk = current;
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restore_fpu(tsk);
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task_thread_info(tsk)->status |= TS_USEDFPU;
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tsk->thread.fpu_counter++;
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}
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void fpu_state_restore(struct pt_regs *regs)
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{
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struct task_struct *tsk = current;
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if (unlikely(!user_mode(regs))) {
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printk(KERN_ERR "BUG: FPU is used in kernel mode.\n");
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BUG();
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return;
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}
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if (!tsk_used_math(tsk)) {
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int ret;
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/*
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* does a slab alloc which can sleep
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*/
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local_irq_enable();
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ret = init_fpu(tsk);
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local_irq_disable();
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if (ret) {
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/*
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* ran out of memory!
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*/
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force_sig(SIGKILL);
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return;
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}
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}
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grab_fpu(regs);
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__fpu_state_restore();
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}
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BUILD_TRAP_HANDLER(fpu_state_restore)
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{
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TRAP_HANDLER_DECL;
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fpu_state_restore(regs);
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}
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#endif /* CONFIG_SH_FPU */
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