From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bruno =?UTF-8?B?UHLDqW1vbnQ=?= Subject: Re: [PATCH] Fix crash in viafb due to 4k stack overflow Date: Fri, 14 Nov 2008 10:01:56 +0100 Message-ID: <20081114100156.4557760c@pluto.restena.lu> References: Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="utf-8" To: JosephChan@via.com.tw Cc: akpm@linux-foundation.org, arjan@infradead.org, linux-fbdev-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, ScottFang@viatech.com.cn Joseph, Are you testing with 4k stacks or with 8k stacks (CONFIG_4KSTACKS)? Note that your failure looks pretty much like the ones I mentionned in http://lkml.org/lkml/2008/11/9/204 It looks like some kernel text/data got corrupted though I have no idea what caused it. For me this kind of NULL pointer dereference did happen a few times then stopped showing up (just a reboot, not kernel change/recompile) Bruno On Fri, 14 Nov 2008 wrote: > After testing the patch with 2.6.28-rc4 kernel, I found something > strange in both viafb built-in and module modes. See the result on my > EPIA-EX (CX700) below. Based on the result, it looks like something > wrong with the new patch. >=20 > Kernel 2.6.28-rc4 + viafb-fix-crash-due-to-4k-stack-overflow.patch >=20 > 1. w/o patching the viafb-fix-crash-due-to-4k-stack-overflow.patch > =3D> System works properly without "kernel panic" issue. >=20 > 2. w/ patching the viafb-fix-crash-due-to-4k-stack-overflow.patch > =3D> System hangs with "kernel panic" randomly after loading the viaf= b > module. Such as: > BUG: unable to handle kernel NULL pointer dereference at 000000c7 > IP: [] rt_worker_func+0xc7/0x15d > Last sysfs file: /sys/class/graphics/fb0/dev > Modules linked in: viafb i2c_algo_bit via_rhine sg pata_via sd_mod > ehci_hcd >=20 > Pid: 6, comm: events/0 Not tainted (2.6.28-rc4b #1) pn test > EIP: 0060:[] EFLAGS: 00010286 CPU:0 > EIP is at rt_worker_func+0xc7/0x15d > ...... > .... > ..... >=20 >=20 > BRs, > Joseph >=20 > -----Original Message----- > From: Joseph Chan=20 > Sent: Thursday, November 13, 2008 8:58 AM > To: 'Andrew Morton'; Bruno Pr=C3=A9mont > Cc: arjan@infradead.org; linux-fbdev-devel@lists.sourceforge.net; > linux-kernel@vger.kernel.org Subject: RE: [PATCH] Fix crash in viafb > due to 4k stack overflow >=20 > I will try this new patch later. :) >=20 > BRs, > Joseph Chan >=20 > -----Original Message----- > From: Andrew Morton [mailto:akpm@linux-foundation.org] > Sent: Thursday, November 13, 2008 7:01 AM > To: Bruno Pr=C3=A9mont > Cc: arjan@infradead.org; Joseph Chan; > linux-fbdev-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org > Subject: Re: [PATCH] Fix crash in viafb due to 4k stack overflow >=20 > On Mon, 10 Nov 2008 22:00:46 +0100 > Bruno Pr__mont wrote: >=20 > > During conversion of viafb_ioctl() I noticed the following: > >=20 > > Those two cases just copy_from_user and do nothing with copied > > data, incomplete implementation?: > > case VIAFB_SET_PANEL_POSITION: > > if (copy_from_user(&u.panel_pos_size_para, argp, > > sizeof(u.panel_pos_size_para))) > > return -EFAULT; > > break; > > case VIAFB_SET_PANEL_SIZE: > > if (copy_from_user(&u.panel_pos_size_para, argp, > > sizeof(u.panel_pos_size_para))) > > return -EFAULT; > > break; > >=20 > > Handling of GET/SET GAMMA looks buggy: > > In each case 256*4 bytes are allocated but only 4 bytes (size of > > pointer) are copied to/from userspace though > > viafb_(get|set)_gamma_table() operates on the full 256 elements... > > case VIAFB_SET_GAMMA_LUT: > > viafb_gamma_table =3D kmalloc(256 * sizeof(u32), > > GFP_KERNEL); if (!viafb_gamma_table) > > return -ENOMEM; > > if (copy_from_user(viafb_gamma_table, argp, > > sizeof(viafb_gamma_table))) { > > kfree(viafb_gamma_table); > > return -EFAULT; > > } > > viafb_set_gamma_table(viafb_bpp, viafb_gamma_table)= ; > > kfree(viafb_gamma_table); > > break; > >=20 > > case VIAFB_GET_GAMMA_LUT: > > viafb_gamma_table =3D kmalloc(256 * sizeof(u32), > > GFP_KERNEL); if (!viafb_gamma_table) > > return -ENOMEM; > > viafb_get_gamma_table(viafb_gamma_table); > > if (copy_to_user(argp, viafb_gamma_table, > > sizeof(viafb_gamma_table))) { > > kfree(viafb_gamma_table); > > return -EFAULT; > > } > > kfree(viafb_gamma_table); > > break; > >=20 > > I don't know if there is a userspace app that uses these VIA > > IOCTLs... so the ioctl part is just compile-tested. > > After checking, fbset just uses some generic framebuffer IOCTLs=20 > > outside of viafb's scope, thus not passing through viafb_ioctl(). > >=20 > >=20 > >=20 > > --- > > --- linux-2.6.28-rc3/drivers/video/via/viafbdev.c.orig > > 2008-11-09 19:36:47.000000000 +0100 +++ > > linux-2.6.28-rc3/drivers/video/via/viafbdev.c 2008-11-10 > > 20:50:32.000000000 +0100 >=20 > hm, OK, I dropped the old patch and merged this one. >=20 > It'd be nice to have it runtime tested and reviewed by Joseph, but we > haven't heard from him yet. viafb might be 8k-stacks-only in 2.6.27, > which would be bad. >=20