This is a note to let you know that I've just added the patch titled
x86/process: Check PF_KTHREAD and not current->mm for kernel threads
to the 5.12-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:
x86-process-check-pf_kthread-and-not-current-mm-for-kernel-threads.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 12f7764ac61200e32c916f038bdc08f884b0b604 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Date: Tue, 8 Jun 2021 16:36:20 +0200
Subject: x86/process: Check PF_KTHREAD and not current->mm for kernel threads
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
commit 12f7764ac61200e32c916f038bdc08f884b0b604 upstream.
switch_fpu_finish() checks current->mm as indicator for kernel threads.
That's wrong because kernel threads can temporarily use a mm of a user
process via kthread_use_mm().
Check the task flags for PF_KTHREAD instead.
Fixes: 0cecca9d03c9 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20210608144345.912645927@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/fpu/internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -578,7 +578,7 @@ static inline void switch_fpu_finish(str
* PKRU state is switched eagerly because it needs to be valid before we
* return to userland e.g. for a copy_to_user() operation.
*/
- if (current->mm) {
+ if (!(current->flags & PF_KTHREAD)) {
pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU);
if (pk)
pkru_val = pk->pkru;
Patches currently in stable-queue which might be from tglx@xxxxxxxxxxxxx are
queue-5.12/x86-process-check-pf_kthread-and-not-current-mm-for-kernel-threads.patch
queue-5.12/x86-pkru-write-hardware-init-value-to-pkru-when-xstate-is-init.patch
queue-5.12/x86-fpu-prevent-state-corruption-in-__fpu__restore_sig.patch
queue-5.12/crash_core-vmcoreinfo-append-section_size_bits-to-vmcoreinfo.patch
queue-5.12/x86-fpu-invalidate-fpu-state-after-a-failed-xrstor-from-a-user-buffer.patch
queue-5.12/x86-fpu-reset-state-for-all-signal-restore-failures.patch
