* [tip: x86/urgent] x86/process: Check PF_KTHREAD and not current->mm for kernel threads
[not found] <20210608144345.912645927@linutronix.de>
@ 2021-06-09 14:46 ` tip-bot2 for Thomas Gleixner
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From: tip-bot2 for Thomas Gleixner @ 2021-06-09 14:46 UTC (permalink / raw)
To: linux-tip-commits
Cc: Thomas Gleixner, Borislav Petkov, Dave Hansen, Rik van Riel,
stable, x86, linux-kernel
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 12f7764ac61200e32c916f038bdc08f884b0b604
Gitweb: https://git.kernel.org/tip/12f7764ac61200e32c916f038bdc08f884b0b604
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Tue, 08 Jun 2021 16:36:20 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Wed, 09 Jun 2021 10:39:04 +02:00
x86/process: Check PF_KTHREAD and not current->mm for kernel threads
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@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144345.912645927@linutronix.de
---
arch/x86/include/asm/fpu/internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index ceeba9f..18382ac 100644
--- 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(struct fpu *new_fpu)
* 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;
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