linux-kernel - Re: potential mem leak when system is low on memory

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Message-ID: <20061017081020.GB1742@ff.dom.local>
Date:	Tue, 17 Oct 2006 10:10:20 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	Amit Choudhary <amit2030@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: potential mem leak when system is low on memory

On 17-10-2006 00:52, Amit Choudhary wrote:
> Hi All,
> 
> I was just scrubbing the kernel for checking the return ststus of
> kmalloc(), and I saw at many places the following things. I just
> wanted to report this.
> 
> 1. If there are more than one kmalloc() calls in the same function,
> and if kmalloc() returns NULL for one of them, then the memory
> obtained from previous kmalloc() calls is not released.
> 
> Something like:
> 
> func()
> {
>    var1 = kmalloc(size);
>    if (!var1)
>         return -ENOMEM;
> 
>    var2 = kmalloc(size);
>    if (!var2)
>         return -ENOMEM;
> 
> /* mem  leak as var1 is not freed */
> 
> }
> 
> 2. Sometimes, memory is allocated in a loop. So, if kmalloc() fails at
> some point, memory allocated previously is not released.
> 
> func()
> {
>    for (i = 0; i < LENGTH; i++) {
>            var1[i] = kmalloc(size);
>            if (!var1[i])
>                 return -ENOMEM;
> 
> /* mem leak as var1[0] to var1[i - 1] is not freed */
> 
>    }
> }
> 
> So, already the system is running low on memory and on top of it there
> are leaks.

So you've found elementary programming bugs and it would
be nice to point this places.

Jarek P.
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