linux-kernel - Re: [Patch 1/2] ia32: use generic sys

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Date:	Tue, 4 Aug 2009 14:24:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [Patch 1/2] ia32: use generic sys_pipe()


* Amerigo Wang <amwang@...hat.com> wrote:

> As suggested by Al, it's better to use the generic sys_pipe() for 
> ia32.
> 
> Signed-off-by: WANG Cong <amwang@...hat.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> CC: Linus Torvalds <torvalds@...ux-foundation.org>

> --- a/arch/x86/ia32/sys_ia32.c
> +++ b/arch/x86/ia32/sys_ia32.c
> @@ -189,20 +189,6 @@ asmlinkage long sys32_mprotect(unsigned long start, size_t len,
>  	return sys_mprotect(start, len, prot);
>  }
>  
> -asmlinkage long sys32_pipe(int __user *fd)
> -{
> -	int retval;
> -	int fds[2];
> -
> -	retval = do_pipe_flags(fds, 0);
> -	if (retval)
> -		goto out;
> -	if (copy_to_user(fd, fds, sizeof(fds)))
> -		retval = -EFAULT;
> -out:
> -	return retval;
> -}

Please _ALWAYS_ mention the change in behavior in the changelog, 
just in case someone ends up bisecting it. I only found out when i 
reviewed the two syscalls out of caution.

The syscall you remove kept stale fd's around in case of -EFAULT 
from copy_to_user(). The generic version does an explicit close of 
those files:

                        sys_close(fd[0]);
                        sys_close(fd[1]);
                        error = -EFAULT;

The generic version looks like the better choice to me but this 
difference should be mentioned in the changelog nevertheless, just 
in case some buggy app runs into this issue.

	Ingo
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