From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 8 Sep 2021 15:29:30 +0200
Subject: x86/fpu/signal: Move xstate clearing out of copy_fpregs_to_sigframe()
Git-commit: fcfb7163329ce832aafef31f26345ef5e8642a17
Patch-mainline: v5.15 or v5.15-rc8 (next release)
References: jsc#SLE-18931
When the direct saving of the FPU registers to the user space sigframe
fails, copy_fpregs_to_sigframe() attempts to clear the user buffer.
The most likely reason for such a fail is a page fault. As
copy_fpregs_to_sigframe() is invoked with pagefaults disabled the chance
that __clear_user() succeeds is minuscule.
Move the clearing out into the caller which replaces the
fault_in_pages_writeable() in that error handling path.
The return value confusion will be cleaned up separately.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210908132525.679356300@linutronix.de
---
arch/x86/kernel/fpu/signal.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 5ca3ce94cf6b..c4abbd97587b 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -136,18 +136,12 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
{
- int err;
-
if (use_xsave())
- err = xsave_to_user_sigframe(buf);
- else if (use_fxsr())
- err = fxsave_to_user_sigframe((struct fxregs_state __user *) buf);
+ return xsave_to_user_sigframe(buf);
+ if (use_fxsr())
+ return fxsave_to_user_sigframe((struct fxregs_state __user *) buf);
else
- err = fnsave_to_user_sigframe((struct fregs_state __user *) buf);
-
- if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
- err = -EFAULT;
- return err;
+ return fnsave_to_user_sigframe((struct fregs_state __user *) buf);
}
/*
@@ -218,9 +212,9 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
fpregs_unlock();
if (ret) {
- if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
+ if (!__clear_user(buf_fx, fpu_user_xstate_size))
goto retry;
- return -EFAULT;
+ return -1;
}
/* Save the fsave header for the 32-bit frames. */