linux-kernel - [RFC PATCH] double free in decompressor.c

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Date:	Fri, 22 Nov 2013 19:50:44 -0200
From:	Geyslan Gregório Bem <geyslan@...il.com>
To:	phillip@...ashfs.org.uk
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] double free in decompressor.c

Coverity caught double free possibility (CID 1130962).

I can patch this, but I have to know if is correct to free comp_opts
in the function squashfs_decompressor_create() or it had to be done in
the caller. My bet is the caller.

128void *squashfs_decompressor_setup(struct super_block *sb, unsigned
short flags)
129{
130        struct squashfs_sb_info *msblk = sb->s_fs_info;
131        void *stream, *comp_opts = get_comp_opts(sb, flags);
132

1. Condition "IS_ERR(comp_opts)", taking false branch
133        if (IS_ERR(comp_opts))
134                return comp_opts;
135

2. freed_arg: "squashfs_decompressor_create(struct squashfs_sb_info *,
void *)" frees "comp_opts".[show details]
136        stream = squashfs_decompressor_create(msblk, comp_opts);

3. Condition "IS_ERR(stream)", taking true branch
137        if (IS_ERR(stream))

CID 1130962 (#1 of 1): Double free (USE_AFTER_FREE)4. double_free:
Calling "kfree(void const *)" frees pointer "comp_opts" which has
already been freed.
138                kfree(comp_opts);
139
140        return stream;
141}

-- 
Regards,

Geyslan G. Bem
hackingbits.com
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