Patch "MIPS: kernel: Clear FPU states when setting up kernel threads" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

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

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-kernel-clear-fpu-states-when-setting-up-kernel-threads.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From a58a173444a68412bb08849bd81c679395f20ca0 Mon Sep 17 00:00:00 2001
From: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Date: Thu, 30 Nov 2023 17:36:01 +0100
Subject: MIPS: kernel: Clear FPU states when setting up kernel threads

From: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Reported-by: Aurelien Jarno <aurel32@xxxxxxxxxx>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1055021
Suggested-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Reviewed-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Signed-off-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/mips/kernel/process.c |   25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -121,6 +121,19 @@ int copy_thread(struct task_struct *p, c
 	/*  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, c
 	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


Patches currently in stable-queue which might be from tsbogend@xxxxxxxxxxxxxxxx are

queue-6.1/mips-kernel-clear-fpu-states-when-setting-up-kernel-threads.patch
queue-6.1/mips-loongson64-handle-more-memory-types-passed-from-firmware.patch
queue-6.1/mips-loongson64-enable-dma-noncoherent-support.patch
queue-6.1/mips-loongson64-reserve-vgabios-memory-on-boot.patch




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