linux-kernel - Re: [PATCH] ext4: Fix invalid free of cache->name after ext4_mb

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Message-ID: <4D3DA7F7.4010306@redhat.com>
Date:	Mon, 24 Jan 2011 10:25:27 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>
CC:	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>
Subject: Re: [PATCH] ext4: Fix invalid free of cache->name after ext4_mb_init()
 error

On 01/24/2011 07:42 AM, Chris Wilson wrote:
> The name allocated for the kmem_cache was being freed in the error path even
> if that name was still assigned to the newly created cache.

This code still has trouble on the module unload / uninit path;
I sent a more invasive patch to just use static patch names,
see [PATCH] ext4: make grpinfo slab cache names static
from last week.

-Eric

> Cc: "Theodore Ts'o" <tytso@....edu>
> Cc: Andreas Dilger <adilger.kernel@...ger.ca>
> Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
> ---
>  fs/ext4/mballoc.c |    5 ++---
>  1 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 851f49b..69b90fe 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2423,7 +2423,6 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
>  	int ret;
>  	int cache_index;
>  	struct kmem_cache *cachep;
> -	char *namep = NULL;
>  
>  	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_offsets);
>  
> @@ -2443,7 +2442,7 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
>  	cache_index = sb->s_blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE;
>  	cachep = ext4_groupinfo_caches[cache_index];
>  	if (!cachep) {
> -		char name[32];
> +		char name[32], *namep;
>  		int len = offsetof(struct ext4_group_info,
>  					bb_counters[sb->s_blocksize_bits + 2]);
>  
> @@ -2459,6 +2458,7 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
>  		cachep = kmem_cache_create(namep, len, 0,
>  					     SLAB_RECLAIM_ACCOUNT, NULL);
>  		if (!cachep) {
> +			kfree(namep);
>  			ret = -ENOMEM;
>  			goto out;
>  		}
> @@ -2520,7 +2520,6 @@ out:
>  	if (ret) {
>  		kfree(sbi->s_mb_offsets);
>  		kfree(sbi->s_mb_maxs);
> -		kfree(namep);
>  	}
>  	return ret;
>  }

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