linux-kernel - Re: [PATCH 4/5] fs: efs: fix possible memory leak

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Message-ID: <20150217193101.GA11847@ZenIV.linux.org.uk>
Date:	Tue, 17 Feb 2015 19:31:01 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] fs: efs: fix possible memory leak

On Thu, Feb 12, 2015 at 02:32:21PM +0530, Sudip Mukherjee wrote:
> we are allocating memory for struct efs_sb_info, but afterwards when
> we are returning with error we are not releasing the memory.

The hell we are not - unlike ->put_super(), ->kill_sb() is *always*
called, even when fill_super() fails halfway through.  Exactly because
it makes for simpler cleanup requirements on failure exits in said
fill_super().  And we have
static void efs_kill_sb(struct super_block *s)
{
        struct efs_sb_info *sbi = SUPER_INFO(s);
        kill_block_super(s);
        kfree(sbi);
}
for ->kill_sb() there, so sbi will *not* leak.

NAK.  This patch not only complicates efs_fill_super() for no good reason,
it ends up with double kfree() on those failure exits - ->s_fs_info is
left pointing to freed memory and efs_kill_sb() does kfree() again.
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