linux-kernel - Re: [PATCH] binfmt_elf_fdpic: Fix clear

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Date:	Wed, 2 Jun 2010 11:40:57 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	David Howells <dhowells@...hat.com>
Cc:	torvalds@...l.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Mike Frysinger <vapier@...too.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH] binfmt_elf_fdpic: Fix clear_user() error handling

David Howells <dhowells@...hat.com> wrote:

> From: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
> 

Thanks for updating, improving, the explanation!

  Takuya


> clear_user() returns the number of bytes that could not be copied rather than
> an error code.  So we should return -EFAULT rather than directly returning the
> results.
> 
> Without this patch, positive values may be returned to elf_fdpic_map_file()
> and the following error handlings do not function as expected.
> 
> 1.
> 	ret = elf_fdpic_map_file_constdisp_on_uclinux(params, file, mm);
> 	if (ret < 0)
> 		return ret;
> 2.
> 	ret = elf_fdpic_map_file_by_direct_mmap(params, file, mm);
> 	if (ret < 0)
> 		return ret;
> 
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
> Signed-off-by: David Howells <dhowells@...hat.com>
> Acked-by: Mike Frysinger <vapier@...too.org>
> CC: Alexander Viro <viro@...iv.linux.org.uk>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: Daisuke HATAYAMA <d.hatayama@...fujitsu.com>
> CC: Paul Mundt <lethal@...ux-sh.org>
> ---
> 
>  fs/binfmt_elf_fdpic.c |   26 +++++++++++---------------
>  1 files changed, 11 insertions(+), 15 deletions(-)
> 
> 
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index 2c5f9a0..63039ed 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -990,10 +990,9 @@ static int elf_fdpic_map_file_constdisp_on_uclinux(
>  
>  		/* clear any space allocated but not loaded */
>  		if (phdr->p_filesz < phdr->p_memsz) {
> -			ret = clear_user((void *) (seg->addr + phdr->p_filesz),
> -					 phdr->p_memsz - phdr->p_filesz);
> -			if (ret)
> -				return ret;
> +			if (clear_user((void *) (seg->addr + phdr->p_filesz),
> +				       phdr->p_memsz - phdr->p_filesz))
> +				return -EFAULT;
>  		}
>  
>  		if (mm) {
> @@ -1027,7 +1026,7 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
>  	struct elf32_fdpic_loadseg *seg;
>  	struct elf32_phdr *phdr;
>  	unsigned long load_addr, delta_vaddr;
> -	int loop, dvset, ret;
> +	int loop, dvset;
>  
>  	load_addr = params->load_addr;
>  	delta_vaddr = 0;
> @@ -1127,9 +1126,8 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
>  		 * PT_LOAD */
>  		if (prot & PROT_WRITE && disp > 0) {
>  			kdebug("clear[%d] ad=%lx sz=%lx", loop, maddr, disp);
> -			ret = clear_user((void __user *) maddr, disp);
> -			if (ret)
> -				return ret;
> +			if (clear_user((void __user *) maddr, disp))
> +				return -EFAULT;
>  			maddr += disp;
>  		}
>  
> @@ -1164,19 +1162,17 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
>  		if (prot & PROT_WRITE && excess1 > 0) {
>  			kdebug("clear[%d] ad=%lx sz=%lx",
>  			       loop, maddr + phdr->p_filesz, excess1);
> -			ret = clear_user((void __user *) maddr + phdr->p_filesz,
> -					 excess1);
> -			if (ret)
> -				return ret;
> +			if (clear_user((void __user *) maddr + phdr->p_filesz,
> +				       excess1))
> +				return -EFAULT;
>  		}
>  
>  #else
>  		if (excess > 0) {
>  			kdebug("clear[%d] ad=%lx sz=%lx",
>  			       loop, maddr + phdr->p_filesz, excess);
> -			ret = clear_user((void *) maddr + phdr->p_filesz, excess);
> -			if (ret)
> -				return ret;
> +			if (clear_user((void *) maddr + phdr->p_filesz, excess))
> +				return -EFAULT;
>  		}
>  #endif
>  
> 


-- 
Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
--
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