[PATCH] race condition in procfs

From: Grzegorz Nosek (grzegorz.nosek_at_gmail.com)
Date: 11/29/05

  • Next message: Michael Krufky: "Re: Linux 2.6.15-rc3" 
    Date:	Tue, 29 Nov 2005 08:17:22 +0100
To: linux-kernel@vger.kernel.org

    Hello,

    I found a race condition in procfs on SMP systems. The result is an
    oops in processes like pidof. Apparently ->proc_read() gets passed a
    potentially NULL pointer. The following micro-patch seems to fix it.

    Best regards,
     Grzegorz Nosek

    --- linux-2.6/fs/proc/base.c.orig 2005-11-25 00:07:43.000000000 +0100
    +++ linux-2.6/fs/proc/base.c 2005-11-28 11:44:11.000000000 +0100
    @@ -718,6 +718,9 @@
           ssize_t length;
           struct task_struct *task = proc_task(inode);

    + if (!task)
    + return -ENOENT;
    +
           if (count > PROC_BLOCK_SIZE)
                   count = PROC_BLOCK_SIZE;
           if (!(page = __get_free_page(GFP_KERNEL)))
    -
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