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    SubjectRe: [PATCH net-next-2.6] net: dev_addr_init() fix

    * Eric Dumazet <dada1@cosmosbay.com> wrote:

    > Eric Dumazet a écrit :
    > > Vegard Nossum a écrit :
    > >> 2009/6/7 John Dykstra <john.dykstra1@gmail.com>:
    > >>> On Sat, 2009-05-30 at 22:23 +0200, Vegard Nossum wrote:
    > >>>> It seems that loopback's hardware address is never initialized by the
    > >>>> kernel. So if userspace attempts to read this address before it has
    > >>>> been set, the kernel will return some uninitialized data (only 6
    > >>>> bytes, though).
    > >>> Thank you for the report, Vegard.
    > >>>
    > >>> I've been unable to reproduce the problem you describe, using
    > >>> 2.6-30-rc8, this test program and a couple of kernel builds for system
    > >>> load:
    > >> [...]
    > >>> ------------------------------------------------------------------
    > >>>
    > >>> Looking at the kernel code, it appears that all bytes of struct
    > >>> net_device, including the L2 address, are initialized to zeros at
    > >>> interface creation time.
    > >>>
    > >>> Can you spot a difference between your test procedures and mine that
    > >>> would enable me to reproduce the problem?
    > >> Hi,
    > >>
    > >> I just tried your test program on a linux-next kernel, it works beautifully :-)
    > >>
    > >> (I made one change: The stack grows downwards on x86, so I think you
    > >> should put child_stack + 16386 as the stack to clone()?)
    > >>
    > >> As I wrote in reply to Stephen Hemminger, this problem seems to be
    > >> caused by a particular patch in linux-next:
    > >>
    > >> commit f001fde5eadd915f4858d22ed70d7040f48767cf
    > >> Author: Jiri Pirko <jpirko@redhat.com>
    > >> Date: Tue May 5 02:48:28 2009 +0000
    > >>
    > >> net: introduce a list of device addresses dev_addr_list (v6)
    > >>
    > >
    > > I believe following patch should fix this problem.
    > >
    > > Thank you
    > >
    > > [PATCH net-next-2.6] net: loopback device dev->addr_len fix
    > >
    > > commit f001fde5eadd915f4858d22ed70d7040f48767cf
    > > (net: introduce a list of device addresses dev_addr_list (v6))
    > > added one regression Vegard Nossum found in its testings.
    > >
    > > loopback device doesnt have a hw address, we should set its
    > > dev->addr_len to 0, not ETH_ALEN.
    > >
    > > Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
    > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    >
    > Oh well, following is probably even more appropriate
    >
    > [PATCH net-next-2.6] net: dev_addr_init() fix
    >
    > commit f001fde5eadd915f4858d22ed70d7040f48767cf
    > (net: introduce a list of device addresses dev_addr_list (v6))
    > added one regression Vegard Nossum found in its testings.
    >
    > dev_addr_init() incorrectly uses sizeof() operator
    >
    > Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
    > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

    Could you please put the word 'kmemcheck' somewhere into the
    changelog, to make git-grepping and historic comparisons easier?

    Thanks,

    Ingo
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