linux-kernel - Possible memory leak in fs/sysfs/bin.c

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Date:	Mon, 6 Jul 2009 23:30:41 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Possible memory leak in fs/sysfs/bin.c

Hi,

I get about 28 (after 1 hour uptime) kmemleak reports like the one below:

unreferenced object 0xc24ab090 (size 4096):
  comm "cat", pid 2930, jiffies 4294902918
  backtrace:
    [<c01e0c3a>] create_object+0xfa/0x250
    [<c01e1e7d>] kmemleak_alloc+0x5d/0x70
    [<c01dbc2d>] __kmalloc_track_caller+0x10d/0x1e0
    [<c01bf5e4>] memdup_user+0x24/0x70
    [<c02394d9>] write+0xb9/0x1b0
    [<c01e480c>] vfs_write+0x9c/0x190
    [<c01e49bd>] sys_write+0x3d/0x70
    [<c010300c>] sysenter_do_call+0x12/0x38
    [<ffffffff>] 0xffffffff

This is the write() function in the file mention in subject. It looks
to me like commit 1c8542c7bb replaced kmalloc() with memdup_user() but
also dropped the kfree(temp). The memdup_user() function allocates
memory but that's never freed in write().

Maybe something like this:

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 9345806..bde6602 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -164,6 +164,7 @@ static ssize_t write(struct file *file, const char
__user *userbuf,
 	mutex_lock(&bb->mutex);

 	memcpy(bb->buffer, temp, count);
+	kfree(temp);

 	count = flush_write(dentry, bb->buffer, offs, count);
 	mutex_unlock(&bb->mutex);

-- 
Catalin
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