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 6.6-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-6.6 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-6.6/mips-kernel-clear-fpu-states-when-setting-up-kernel-threads.patch
queue-6.6/mips-loongson64-handle-more-memory-types-passed-from-firmware.patch
queue-6.6/mips-loongson64-enable-dma-noncoherent-support.patch
queue-6.6/mips-loongson64-reserve-vgabios-memory-on-boot.patch
