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Date: Sat, 19 May 2007 23:41:38 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Akinobu Mita <akinobu.mita@gmail.com>
Cc: linux-kernel@vger.kernel.org, stable@kernel.org,
       Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] check d_path() error in print-fatal-signals
Message-Id: <20070519234138.a800e0fb.akpm@linux-foundation.org>
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On Sun, 20 May 2007 14:56:39 +0900 Akinobu Mita <akinobu.mita@gmail.com> wrote:

> d_path() returns -ENAMETOOLONG if buffer length is not enough.
> But there is no error handling for it in print_vma() which calls
> d_path() with not enough buffer (We can easily make segfault program
> which has longer path than 128bytes).
> 
> This patch allocates enough buffer for d_path() dynamically.
> audit_log_d_path() is doing sililar thing. So I just stole from it.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> 
> ---
>  kernel/signal.c |   10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> Index: 2.6-mm/kernel/signal.c
> ===================================================================
> --- 2.6-mm.orig/kernel/signal.c
> +++ 2.6-mm/kernel/signal.c
> @@ -740,15 +740,23 @@ static int print_vma(struct vm_area_stru
>  	 * special [heap] marker for the heap:
>  	 */
>  	if (file) {
> -#define SIZE 128
> -		char tmp[SIZE], *str;
> -
> -		str = d_path(file->f_dentry, file->f_vfsmnt, tmp, SIZE);
> -		while (str[0] && (str[0] == ' '))
> -			str++;
> +		char *p, *path;
>  
> +		/* We will allow 11 spaces for ' (deleted)' to be appended */
> +		path = kmalloc(PATH_MAX + 11, GFP_KERNEL);
> +		if (!path)
> +			p = "<no memory>";
> +		else {
> +			p = d_path(file->f_dentry, file->f_vfsmnt, path,
> +				   PATH_MAX + 11);
> +			if (IS_ERR(p))
> +				p = "<too long>";
> +			else
> +				p = strstrip(p);
> +		}
>  		pad_len_spaces(len);
> -		printk("%s", str);
> +		printk("%s", p);
> +		kfree(path);
>  	} else {
>  		const char *name = arch_vma_name(vma);
>  		if (!name) {

Thanks.

This bug exists only in -mm kernels, and is introduced by the -mm-only
debugging patch
vdso-improve-print_fatal_signals-support-by-adding-memory-maps.patch.

I think I'll just drop that patch - I don't think it is proving useful to
anyone.