Bug_reply : Out of range ptr error in module indicates bug in slab.c

From: selvakumar nagendran (kernelselva_at_yahoo.com)
Date: 12/30/04

  • Next message: Arjan van de Ven: "Re: Bug_reply : Out of range ptr error in module indicates bug in slab.c" 
    Date:	Thu, 30 Dec 2004 04:13:10 -0800 (PST)
To: Arjan van de Ven <arjan@infradead.org>

     Hello,
         Thanks for ur help. The user will be changing
    this using system calls like dup,dup2 etc. If I keep
    track of all these modifications by intercepting all
    those syscalls and use inode number for identifying
    the structure uniquely, will it break?

    Thanks,
    selva

    > nagendran wrote:
    > > else {
    > > new -> pipe_read_end = fdes[0];
    > > new -> pipe_write_end = fdes[1];
    >
    > this is a bug; fdes is a USERSPACE pointer, you
    > cannot directly access
    > that from kernel space, you need to use
    > copy_from_user() for that.
    >
    > And note, what you are doing is unreliable, since
    > the user is capable of
    > changing that information before you log it in your
    > structure, so if you
    > want to use the data you log for anything security
    > related or for
    > something that has to be accurate, it's broken...
    >
    > > while(temp != NULL)
    > > {
    > > kfree(temp);
    > > temp = temp -> next;
    > > }
    >
    > that is of course wrong; you free temp and THEN you
    > access it!!
    >
    >
    > -
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