* Re: 2.6.34 Crash in dmaengine_put() [not found] ` <AANLkTimsDSrEL8vT877pLYSa4A338p4Y8w0Ya6Xm7BFJ@mail.gmail.com> @ 2010-06-22 14:43 ` Eric Dumazet 2010-06-22 16:36 ` Jeffrey Merkey 0 siblings, 1 reply; 2+ messages in thread From: Eric Dumazet @ 2010-06-22 14:43 UTC (permalink / raw) To: Jeffrey Merkey; +Cc: Andrew Morton, linux-kernel, Dan Williams, netdev Le mardi 22 juin 2010 à 08:08 -0600, Jeffrey Merkey a écrit : Please dont top post on lkml (or netdev) messages > OK. This bug occurs if you OR in the IFF_UP flag while creating > virtual interfaces without going through the normal ifup/ifdown > scripts. Looks like a hole. I will post the trace shortly. It's > easy to reproduce, take the dummy net driver, OR in the IFF_UP flag in > dummy_setup, and watch the kernel crash. > Then dont do that ? No need to send us a trace, unless you use a pristine kernel. IFF_UP changes rules are very strict, dont try to avoid them and claim there is a hole or something wrong. Check __dev_open() , __dev_close() and __dev_change_flags() were OR/AND IFF_UP is done by core network. Net drivers are not allowed to change IFF_UP themselves. (DE-600 & DE-620 being the exceptions to confirm this rule, of course) > Jeff > > On Mon, Jun 21, 2010 at 9:28 PM, Andrew Morton > <akpm@linux-foundation.org> wrote: > > On Mon, 21 Jun 2010 20:57:40 -0600 Jeffrey Merkey <jeffmerkey@gmail.com> wrote: > > > >> If someone sets the IFF_UP flags in the netdev structure without going > >> through ifup userspace stuff, during unregister of the the netdev > >> the dmaengine-put code will decrement the reference counter negative, > >> and crash at BUG! in the driver/dma/dmaengine.c code. This seems > >> busted. > >> > > > > Please send a copy of the kernel BUG trace. > > > - ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: 2.6.34 Crash in dmaengine_put() 2010-06-22 14:43 ` 2.6.34 Crash in dmaengine_put() Eric Dumazet @ 2010-06-22 16:36 ` Jeffrey Merkey 0 siblings, 0 replies; 2+ messages in thread From: Jeffrey Merkey @ 2010-06-22 16:36 UTC (permalink / raw) To: Eric Dumazet; +Cc: Andrew Morton, linux-kernel, Dan Williams, netdev > >> OK. This bug occurs if you OR in the IFF_UP flag while creating >> virtual interfaces without going through the normal ifup/ifdown >> scripts. Looks like a hole. I will post the trace shortly. It's >> easy to reproduce, take the dummy net driver, OR in the IFF_UP flag in >> dummy_setup, and watch the kernel crash. >> > > Then dont do that ? > > No need to send us a trace, unless you use a pristine kernel. > > IFF_UP changes rules are very strict, dont try to avoid them and claim > there is a hole or something wrong. > > Check __dev_open() , __dev_close() and __dev_change_flags() were OR/AND > IFF_UP is done by core network. > > Net drivers are not allowed to change IFF_UP themselves. > > (DE-600 & DE-620 being the exceptions to confirm this rule, of course) > Gee. OK, its a bug. I see the crash when unregister_netdev is called. Changing a flag in a driver should not cause the kernel to crash. You should check the code. The dmaengine registration should have nothing to do with registering a netdev -- period. I have coded arounnd it but its damn convenient to create virtual drivers on the fly and mark them as UP without needing to configure a bunch of text scripts to bring one up or down. The code itself is busted because it has a check if the dmaengine ref count goes negative. If you are going to have a registration layer the rest of the OS should not have to wonder about its disconnected state. The busted code is right at the top of dmaengine_put where it decrements the ref count then immediately jumps to a bug. Need a better way here I think to prevent needless crashes. Someone could just alter this flag remotely and crash a server -- HOLE - :) Jeff ^ permalink raw reply [flat|nested] 2+ messages in thread
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2010-06-22 14:43 ` 2.6.34 Crash in dmaengine_put() Eric Dumazet
2010-06-22 16:36 ` Jeffrey Merkey
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