linux-ext4 - Re: [PATCH] ext4: fix null pointer deref on mount

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Message-ID: <4977C124.5030102@ph.tum.de>
Date:	Thu, 22 Jan 2009 01:43:16 +0100
From:	Thiemo Nagel <thiemo.nagel@...tum.de>
To:	Theodore Tso <tytso@....edu>
CC:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix null pointer deref on mount

Dear Ted,

one (hopefully) last thing about this patch:

>  	blocks_count = (ext4_blocks_count(es) -
>  			le32_to_cpu(es->s_first_data_block) +
>  			EXT4_BLOCKS_PER_GROUP(sb) - 1);
>  	do_div(blocks_count, EXT4_BLOCKS_PER_GROUP(sb));
> +	if (blocks_count > ((uint64_t)1<<32) - EXT4_DESC_PER_BLOCK(sb)) {
> +		printk(KERN_WARNING "EXT4-fs: groups count too large: %u "
> +		       "(block count %llu, first data block %u, "
> +		       "blocks per group %lu)\n", sbi->s_groups_count,
> +		       ext4_blocks_count(es),
> +		       le32_to_cpu(es->s_first_data_block),
> +		       EXT4_BLOCKS_PER_GROUP(sb));
> +		goto failed_mount;
> +	}
>  	sbi->s_groups_count = blocks_count;
>  	db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
>  		   EXT4_DESC_PER_BLOCK(sb);

When you printk() sbi->s_groups_count it is not yet initialised, I think 
blocks_count should be used there instead.

Kind regards,

Thiemo
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