Re: [PATCH] - fix oops in sysfs_readdir

[Chris Wright <chrisw@sous-sol.org>]

[Please Cc: Adrian Bunk (added) for 2.6.16-stable material]

* Eric Sandeen (sandeen@redhat.com) wrote:
> This is a non-ida backport of Tejun's patch in -mm at:
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc1/2.6.22-rc1-mm1/broken-out/gregkh-driver-sysfs-allocate-inode-number-using-ida.patch
> for the 2.6.16 -stable tree - it follows the same scheme of using s_ino to safely
> store & retrieve the inode number of sysfs entries for use in sysfs_readdir,
> but uses a brain-dead-simple inode nr allocator rather than ida, which would
> bring along a lot of newer, more complex code.
> 
> No, this doesn't guarantee uniqueness of sysfs inode numbers, but then
> the code in -stable today doesn't either - and with this change, at least
> it shouldn't oops.
> 
> Comments?
> 
> Thanks,
> 
> -Eric
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> 
> Index: linux-2.6.16.51/fs/sysfs/dir.c
> ===================================================================
> --- linux-2.6.16.51.orig/fs/sysfs/dir.c
> +++ linux-2.6.16.51/fs/sysfs/dir.c
> @@ -29,6 +29,14 @@ static struct dentry_operations sysfs_de
>  	.d_iput		= sysfs_d_iput,
>  };
>  
> +static unsigned int sysfs_inode_counter;
> +ino_t sysfs_get_inum(void)
> +{
> +	if (unlikely(sysfs_inode_counter < 3))
> +		sysfs_inode_counter = 3;
> +	return sysfs_inode_counter++;
> +}
> +
>  /*
>   * Allocates a new sysfs_dirent and links it to the parent sysfs_dirent
>   */
> @@ -385,7 +393,7 @@ static int sysfs_readdir(struct file * f
>  
>  	switch (i) {
>  		case 0:
> -			ino = dentry->d_inode->i_ino;
> +			ino = parent_sd->s_ino;
>  			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
>  				break;
>  			filp->f_pos++;
> @@ -415,10 +423,7 @@ static int sysfs_readdir(struct file * f
>  
>  				name = sysfs_get_name(next);
>  				len = strlen(name);
> -				if (next->s_dentry)
> -					ino = next->s_dentry->d_inode->i_ino;
> -				else
> -					ino = iunique(sysfs_sb, 2);
> +				ino = next->s_ino;
>  
>  				if (filldir(dirent, name, len, filp->f_pos, ino,
>  						 dt_type(next)) < 0)
> Index: linux-2.6.16.51/fs/sysfs/inode.c
> ===================================================================
> --- linux-2.6.16.51.orig/fs/sysfs/inode.c
> +++ linux-2.6.16.51/fs/sysfs/inode.c
> @@ -119,6 +119,7 @@ struct inode * sysfs_new_inode(mode_t mo
>  		inode->i_mapping->a_ops = &sysfs_aops;
>  		inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
>  		inode->i_op = &sysfs_inode_operations;
> +		inode->i_ino = sd->s_ino;
>  
>  		if (sd->s_iattr) {
>  			/* sysfs_dirent has non-default attributes
> Index: linux-2.6.16.51/fs/sysfs/mount.c
> ===================================================================
> --- linux-2.6.16.51.orig/fs/sysfs/mount.c
> +++ linux-2.6.16.51/fs/sysfs/mount.c
> @@ -29,6 +29,7 @@ static struct sysfs_dirent sysfs_root = 
>  	.s_element	= NULL,
>  	.s_type		= SYSFS_ROOT,
>  	.s_iattr	= NULL,
> +	.s_ino		= 1,
>  };
>  
>  static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
> Index: linux-2.6.16.51/include/linux/sysfs.h
> ===================================================================
> --- linux-2.6.16.51.orig/include/linux/sysfs.h
> +++ linux-2.6.16.51/include/linux/sysfs.h
> @@ -72,6 +72,7 @@ struct sysfs_dirent {
>  	void 			* s_element;
>  	int			s_type;
>  	umode_t			s_mode;
> +	ino_t			s_ino;
>  	struct dentry		* s_dentry;
>  	struct iattr		* s_iattr;
>  };
-
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