MIPS: kernel: Clear FPU states when setting up kernel threads

commit a58a173444a68412bb08849bd81c679395f20ca0 upstream.

io_uring sets up the io worker kernel thread via a syscall out of an
user space prrocess. This process might have used FPU and since
copy_thread() didn't clear FPU states for kernel threads a BUG()
is triggered for using FPU inside kernel. Move code around
to always clear FPU state for user and kernel threads.

Cc: stable@vger.kernel.org
Reported-by: Aurelien Jarno <aurel32@debian.org>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1055021
Suggested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index bbe9ce4..17d80e2 100644 (file)
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -121,6 +121,19 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
        /*  Put the stack after the struct pt_regs.  */
        childksp = (unsigned long) childregs;
        p->thread.cp0_status = (read_c0_status() & ~(ST0_CU2|ST0_CU1)) | ST0_KERNEL_CUMASK;
+
+       /*
+        * New tasks lose permission to use the fpu. This accelerates context
+        * switching for most programs since they don't use the fpu.
+        */
+       clear_tsk_thread_flag(p, TIF_USEDFPU);
+       clear_tsk_thread_flag(p, TIF_USEDMSA);
+       clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
+
+#ifdef CONFIG_MIPS_MT_FPAFF
+       clear_tsk_thread_flag(p, TIF_FPUBOUND);
+#endif /* CONFIG_MIPS_MT_FPAFF */
+
        if (unlikely(args->fn)) {
                /* kernel thread */
                unsigned long status = p->thread.cp0_status;
@@ -149,20 +162,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
        p->thread.reg29 = (unsigned long) childregs;
        p->thread.reg31 = (unsigned long) ret_from_fork;
 
-       /*
-        * New tasks lose permission to use the fpu. This accelerates context
-        * switching for most programs since they don't use the fpu.
-        */
        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 
-       clear_tsk_thread_flag(p, TIF_USEDFPU);
-       clear_tsk_thread_flag(p, TIF_USEDMSA);
-       clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
-
-#ifdef CONFIG_MIPS_MT_FPAFF
-       clear_tsk_thread_flag(p, TIF_FPUBOUND);
-#endif /* CONFIG_MIPS_MT_FPAFF */
-
 #ifdef CONFIG_MIPS_FP_SUPPORT
        atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);
 #endif