Messages in this thread Patch in this message | | | Date | Mon, 08 Jun 2009 15:49:24 +0200 | From | Eric Dumazet <> | Subject | Re: [PATCH net-next-2.6] net: dev_addr_init() fix |
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Ingo Molnar a écrit : > * 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? >
Sure I can do that, giving me opportunity to use my current email address, since dada1@cosmosbay.com will disappear shortly.
Thank you
[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.
With kmemcheck help, Vegard found some uninitialized memory was read and reported to user, potentialy leaking kernel data. ( thread can be found on http://lkml.org/lkml/2009/5/30/177 )
dev_addr_init() incorrectly uses sizeof() operator. We were initializing one byte instead of MAX_ADDR_LEN bytes.
Reported-by: Vegard Nossum <vegard.nossum@gmail.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Jiri Pirko <jpirko@redhat.com> ---
diff --git a/net/core/dev.c b/net/core/dev.c index 1f38401..65387d9 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3655,8 +3655,8 @@ static int dev_addr_init(struct net_device *dev) /* rtnl_mutex must be held here */ INIT_LIST_HEAD(&dev->dev_addr_list); - memset(addr, 0, sizeof(*addr)); - err = __hw_addr_add(&dev->dev_addr_list, NULL, addr, sizeof(*addr), + memset(addr, 0, sizeof(addr)); + err = __hw_addr_add(&dev->dev_addr_list, NULL, addr, sizeof(addr), NETDEV_HW_ADDR_T_LAN); if (!err) { /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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