diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2019-02-14 10:30:52 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-21 18:48:56 +0200 |
| commit | 45fe6deee2f2b8889368c5fa5ac832b571c6ea52 (patch) | |
| tree | b2a27d7a891c7bba324a157d2aba3de4ad8350fa /arch/x86/include | |
| parent | 621881dfdad1e64705ab17987802f1bba47c575f (diff) | |
sched/x86: Save [ER]FLAGS on context switch
commit 6690e86be83ac75832e461c141055b5d601c0a6d upstream.
Effectively reverts commit:
2c7577a75837 ("sched/x86_64: Don't save flags on context switch")
Specifically because SMAP uses FLAGS.AC which invalidates the claim
that the kernel has clean flags.
In particular; while preemption from interrupt return is fine (the
IRET frame on the exception stack contains FLAGS) it breaks any code
that does synchonous scheduling, including preempt_enable().
This has become a significant issue ever since commit:
5b24a7a2aa20 ("Add 'unsafe' user access functions for batched accesses")
provided for means of having 'normal' C code between STAC / CLAC,
exposing the FLAGS.AC state. So far this hasn't led to trouble,
however fix it before it comes apart.
Reported-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
Fixes: 5b24a7a2aa20 ("Add 'unsafe' user access functions for batched accesses")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/switch_to.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index 676e84f521ba..e959b8d40473 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -35,6 +35,7 @@ asmlinkage void ret_from_fork(void); /* data that is pointed to by thread.sp */ struct inactive_task_frame { + unsigned long flags; #ifdef CONFIG_X86_64 unsigned long r15; unsigned long r14; |