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x86/fpu/signal: Move xstate clearing out of copy_fpregs_to_sigframe() 

commit fcfb716332 upstream.

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
Signed-off-by: Chen Zhuo <sagazchen@tencent.com>
Signed-off-by: Xinghui Li <korantli@tencent.com>
This commit is contained in:
Thomas Gleixner 2021-09-08 15:29:30 +02:00 committed by Jianping Liu
parent b99f02b5b3
commit 720454b531
1 changed files with 6 additions and 12 deletions
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18
arch/x86/kernel/fpu/signal.c
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@ -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 @@ retry:
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. */