Messages in this thread | | | Date | Fri, 24 Aug 2007 23:52:08 -0400 | From | Mathieu Desnoyers <> | Subject | Re: kernel BUG with 2.6.23-rc3-mm1: skb_over_panic |
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* Kay Sievers (kay.sievers@vrfy.org) wrote: > On Fri, 2007-08-24 at 23:02 -0400, Mathieu Desnoyers wrote: > > * Greg KH (greg@kroah.com) wrote: > > > On Fri, Aug 24, 2007 at 05:44:50PM -0700, Andrew Morton wrote: > > > > On Fri, 24 Aug 2007 20:16:38 -0400 > > > > Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote: > > > > > > > > > * Andrew Morton (akpm@linux-foundation.org) wrote: > > > > > > On Fri, 24 Aug 2007 18:47:07 -0400 > > > > > > Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote: > > > > > > > > > > > > > Hi Andrew, > > > > > > > > > > > > > > I get the following BUG when booting 2.6.23-rc3-mm1 on i386. I wonder if > > > > > > > you would have some ideas about what is causing this problem. I'll start > > > > > > > bissecting it soon. I seems to be caused by an buggy skb_put call in > > > > > > > kobject_uevent_env. > > > > > > > hm, don't know, sorry. Kay fixed a few things in there, but iirc pretty > > > > > > much all of the fixes were in rc3-mm1 anyway. > > > > > > > > > > > > I doubt if bisection will tell us a lot: it'll probably point at > > > > > > gregkh-driver-driver-core-change-add_uevent_var-to-use-a-struct.patch. > > > > > > > > > > > > What we _would_ like to know is which sysfs file is being written to. We > > > > > > used to have a debug patch to exactly address this problem but it got > > > > > > transferred into Greg's tree from whence it mysteriously disappeared. > > > > > > > > > > > > > > > > Ok, here it is: > > > > > > > > > > filename : > > > > > > > > > > /devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/rev > > > > > > > > Bah. I've never found a sane way of going from a sysfs pathname back to the > > > > code which implements that pathname :( > > > > > > > > <greps the tree for '"rev"'> > > > > > > > > <comes up with zilch> > > > > > > It's a scsi file, as the above is a scsi device. It's created in the > > > drivers/scsi/scsi_sysfs.c file. > > > I think I am slowly getting there.. it looks like an off-by-one in > > lib/kobject_uevent.c: add_uevent_var > > > > when testing the return value of vsnprintf > > > > if (len + 1 >= (sizeof(env->buf) - env->buflen)) > > > > should be > > > > if (len >= (sizeof(env->buf) - env->buflen)) > > > > And then the problem underneath is that the array is too short for some > > values. > > That should be changed, yes. But we should not reach the end of the > buffer. > > > Since the return value of add_uevent_var is always ignored (why?) > > Because nobody added these checks, most of the callers check, some > don't. We should fix that step by step, sure. > > > from its callers, fixing the off-by-one will just fail silently, which is > > almost worse. > > > > I think we should find some better way of handling full static arrays. > > > > And the bug is still there even if I fix these. So I'll continue my > > investigation. > > Yeah, before these changes it was the environment buffer which got > corrupted, but seems nobody noticed it. Now it triggers BUG() if we run > into problems. > > This needs a fix. It may be the reason for the too small buffer, you are > seeing. > > Thanks, > Kay > > --- a/drivers/firmware/dmi-id.c > +++ b/drivers/firmware/dmi-id.c > @@ -155,6 +155,7 @@ static int dmi_dev_uevent(struct device *dev, struct kobj_uevent_env *env) > sizeof(env->buf) - env->buflen); > if (len >= (sizeof(env->buf) - env->buflen)) > return -ENOMEM; > + env->buflen += len; > return 0; > } > >
Yep, adding some printks, it points in that direction:
[ 179.898618] DBG string ACTION=add [ 179.908565] put DBG 1 len 22 envlen 68 [ 179.919807] DBG string DEVPATH=/class/dmi/id [ 179.921584] DBG req size 836 [ 179.921588] DBG ali size 864 [ 179.921632] DBG req size 836 [ 179.921634] DBG ali size 864 [ 179.966998] put DBG 2 len 14 envlen 68 [ 179.978208] DBG string SUBSYSTEM=dmi [ 179.988901] put DBG 3 len 21 envlen 68 [ 180.000109] DBG string MODALIAS=dSEQNUM=971
as we can see, MODALIAS=d is clearly wrong there and should have a \0. This is why the skb_put goes over the end of the allocated skb.
[ 180.012618] put DBG 4 len 11 envlen 68 [ 180.023829] DBG string SEQNUM=971 [ 180.033742] skb_over_panic: text:c0252ee8 len:97 put:11 head:c2afa200 data:c2afa200 tail:0xc2afa261 end:0xc2afa260 dev:<NULL> [ 180.067545] ------------[ cut here ]------------ [ 180.081341] Kernel BUG at c039e1bc [verbose debug info unavailable] [ 180.100069] invalid opcode: 0000 [#1] PREEMPT SMP
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - 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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