Commit-ID: aab8445c4e1cceeb3f739352041ec1c2586bc923
Gitweb: https://git.kernel.org/tip/aab8445c4e1cceeb3f739352041ec1c2586bc923
Author: Sebastian Andrzej Siewior <[email protected]>
AuthorDate: Fri, 7 Jun 2019 16:29:16 +0200
Committer: Borislav Petkov <[email protected]>
CommitDate: Sat, 8 Jun 2019 11:45:15 +0200
x86/fpu: Update kernel's FPU state before using for the fsave header
In commit
39388e80f9b0c ("x86/fpu: Don't save fxregs for ia32 frames in
copy_fpstate_to_sigframe()")
I removed the statement
| if (ia32_fxstate)
| copy_fxregs_to_kernel(fpu);
and argued that it was wrongly merged because the content was already
saved in kernel's state.
This was wrong: It is required to write it back because it is only
saved on the user-stack and save_fsave_header() reads it from task's
FPU-state. I missed that part…
Save x87 FPU state unless thread's FPU registers are already up to date.
Fixes: 39388e80f9b0c ("x86/fpu: Don't save fxregs for ia32 frames in
copy_fpstate_to_sigframe()")
Reported-by: Eric Biggers <[email protected]>
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Tested-by: Eric Biggers <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: "Jason A. Donenfeld" <[email protected]>
Cc: kvm ML <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/kernel/fpu/signal.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 060d6188b453..0071b794ed19 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -62,6 +62,11 @@ static inline int save_fsave_header(struct task_struct *tsk,
void __user *buf)
struct user_i387_ia32_struct env;
struct _fpstate_32 __user *fp = buf;
+ fpregs_lock();
+ if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+ copy_fxregs_to_kernel(&tsk->thread.fpu);
+ fpregs_unlock();
+
convert_from_fxsr(&env, tsk);
if (__copy_to_user(buf, &env, sizeof(env)) ||
