summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/fpu
diff options
context:
space:
mode:
authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2019-12-20 22:59:06 +0300
committerBorislav Petkov <bp@suse.de>2020-01-07 15:44:42 +0300
commitbbc55341b9c67645d1a5471506370caf7dd4a203 (patch)
treed8a5686849d1b7f1b9f8f167183754c92b6657b4 /arch/x86/kernel/fpu
parent158e2ee61f22b878d61de92bea5aad3d2df1c146 (diff)
downloadlinux-bbc55341b9c67645d1a5471506370caf7dd4a203.tar.xz
x86/fpu: Deactivate FPU state after failure during state load
In __fpu__restore_sig(), fpu_fpregs_owner_ctx needs to be reset if the FPU state was not fully restored. Otherwise the following may happen (on the same CPU): Task A Task B fpu_fpregs_owner_ctx *active* A.fpu __fpu__restore_sig() ctx switch load B.fpu *active* B.fpu fpregs_lock() copy_user_to_fpregs_zeroing() copy_kernel_to_xregs() *modify* copy_user_to_xregs() *fails* fpregs_unlock() ctx switch skip loading B.fpu, *active* B.fpu In the success case, fpu_fpregs_owner_ctx is set to the current task. In the failure case, the FPU state might have been modified by loading the init state. In this case, fpu_fpregs_owner_ctx needs to be reset in order to ensure that the FPU state of the following task is loaded from saved state (and not skipped because it was the previous state). Reset fpu_fpregs_owner_ctx after a failure during restore occurred, to ensure that the FPU state for the next task is always loaded. The problem was debugged-by Yu-cheng Yu <yu-cheng.yu@intel.com>. [ bp: Massage commit message. ] Fixes: 5f409e20b7945 ("x86/fpu: Defer FPU state load until return to userspace") Reported-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20191220195906.plk6kpmsrikvbcfn@linutronix.de
Diffstat (limited to 'arch/x86/kernel/fpu')
-rw-r--r--arch/x86/kernel/fpu/signal.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 0071b794ed19..400a05e1c1c5 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -352,6 +352,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
fpregs_unlock();
return 0;
}
+ fpregs_deactivate(fpu);
fpregs_unlock();
}
@@ -403,6 +404,8 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
}
if (!ret)
fpregs_mark_activate();
+ else
+ fpregs_deactivate(fpu);
fpregs_unlock();
err_out: