Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753956AbXJWSph (ORCPT ); Tue, 23 Oct 2007 14:45:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752425AbXJWSpV (ORCPT ); Tue, 23 Oct 2007 14:45:21 -0400 Received: from brick.kernel.dk ([87.55.233.238]:8392 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752454AbXJWSpT (ORCPT ); Tue, 23 Oct 2007 14:45:19 -0400 Date: Tue, 23 Oct 2007 20:45:14 +0200 From: Jens Axboe To: Jean Delvare Cc: Florin Iucha , Linux Kernel Mailing List Subject: Re: kernel NULL pointer dereference in blk_rq_map_sg with v2.6.23-6815-g0895e91 Message-ID: <20071023184514.GF14671@kernel.dk> References: <20071023124637.GJ7918@iucha.net> <20071023124738.GW5059@kernel.dk> <20071023162850.0b76e410@hyperion.delvare> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071023162850.0b76e410@hyperion.delvare> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6553 Lines: 125 On Tue, Oct 23 2007, Jean Delvare wrote: > Hi Jens, > > On Tue, 23 Oct 2007 14:47:38 +0200, Jens Axboe wrote: > > On Tue, Oct 23 2007, Florin Iucha wrote: > > > Jens, > > > > > > This is freshly after booting into this morning's kernel: > > > > > > [ 60.656136] Unable to handle kernel NULL pointer dereference at 0000000000000000 RIP: > > > [ 60.656143] [] blk_rq_map_sg+0x10d/0x17c > > > [ 60.656151] PGD 4640067 PUD 46d4067 PMD 0 > > > [ 60.656154] Oops: 0000 [1] SMP > > > [ 60.656157] CPU 1 > > > [ 60.656159] Modules linked in: sbp2 lp dvb_pll lgdt330x cx88_dvb cx88_vp3054_i2c videobuf_dvb tuner tea5767 td > > > a8290 tuner_simple mt20xx cx88_alsa cx8802 cx8800 cx88xx ir_common tveeprom videobuf_dma_sg videobuf_core btcx_ri > > > sc i2c_nforce2 evdev rtc forcedeth ehci_hcd fuse > > > [ 60.656176] Pid: 4250, comm: hald-probe-stor Not tainted 2.6.24-rc0-5 #1 > > > [ 60.656178] RIP: 0010:[] [] blk_rq_map_sg+0x10d/0x17c > > > [ 60.656182] RSP: 0018:ffff810004791930 EFLAGS: 00010246 > > > [ 60.656184] RAX: 000000000403b000 RBX: 0000000000001000 RCX: 6db6db6db6db6db7 > > > [ 60.656187] RDX: 0000000000000000 RSI: ffff810001000000 RDI: 0000000005701000 > > > [ 60.656189] RBP: ffff810004791968 R08: 0000000005700000 R09: ffff8100044aa060 > > > [ 60.656191] R10: 0000000000000000 R11: ffff8100050dea00 R12: 0000000000002000 > > > [ 60.656193] R13: ffff8100060d2700 R14: 0000000000000000 R15: ffffffff807f0000 > > > [ 60.656196] FS: 00002b5da088e6e0(0000) GS:ffff810003011500(0000) knlGS:0000000000000000 > > > [ 60.656198] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > > > [ 60.656200] CR2: 0000000000000000 CR3: 0000000004568000 CR4: 00000000000006e0 > > > [ 60.656202] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > [ 60.656204] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > > > [ 60.656207] Process hald-probe-stor (pid: 4250, threadinfo ffff810004790000, task ffff810006312000) > > > [ 60.656208] Stack: ffff81000607a000 0000000100000001 ffff8100040fa120 ffffffff807fe2c0 > > > [ 60.656213] ffff81000607a000 ffff81000607a000 ffffffff807fe2c0 ffff8100047919a8 > > > [ 60.656217] ffffffff8041bb58 ffff8100047919a8 ffff8100040fa120 ffffffff807fe2c0 > > > [ 60.656220] Call Trace: > > > [ 60.656226] [] ide_map_sg+0x38/0xb0 > > > [ 60.656231] [] cdrom_start_read_continuation+0x0/0xb5 > > > [ 60.656234] [] ide_build_sglist+0x38/0x88 > > > [ 60.656238] [] ide_build_dmatable+0x2f/0x172 > > > [ 60.656241] [] ide_dma_setup+0x34/0xaa > > > [ 60.656245] [] cdrom_start_packet_command+0x5a/0x177 > > > [ 60.656249] [] cfq_dispatch_insert+0x38/0x50 > > > [ 60.656253] [] ide_do_rw_cdrom+0x423/0x57c > > > [ 60.656257] [] ide_do_request+0x7a7/0xa74 > > > [ 60.656263] [] del_timer+0x52/0x5d > > > [ 60.656267] [] sync_page+0x0/0x45 > > > [ 60.656269] [] do_ide_request+0x1b/0x1d > > > [ 60.656273] [] __generic_unplug_device+0x28/0x2c > > > [ 60.656276] [] generic_unplug_device+0x20/0x31 > > > [ 60.656279] [] blk_backing_dev_unplug+0x16/0x18 > > > [ 60.656283] [] block_sync_page+0x42/0x44 > > > [ 60.656285] [] sync_page+0x3c/0x45 > > > [ 60.656290] [] __wait_on_bit_lock+0x42/0x79 > > > [ 60.656294] [] __lock_page+0x64/0x6b > > > [ 60.656298] [] wake_bit_function+0x0/0x2a > > > [ 60.656301] [] do_generic_mapping_read+0x1da/0x383 > > > [ 60.656304] [] file_read_actor+0x0/0x137 > > > [ 60.656309] [] generic_file_aio_read+0x11e/0x15d > > > [ 60.656315] [] do_sync_read+0xe2/0x126 > > > [ 60.656318] [] handle_mm_fault+0x62e/0x65e > > > [ 60.656324] [] __up_read+0x8f/0x97 > > > [ 60.656327] [] autoremove_wake_function+0x0/0x38 > > > [ 60.656331] [] __mutex_lock_slowpath+0x22f/0x23c > > > [ 60.656337] [] vfs_read+0xab/0x134 > > > [ 60.656341] [] sys_read+0x47/0x6f > > > [ 60.656345] [] system_call+0x7e/0x83 > > > [ 60.656349] > > > [ 60.656350] > > > [ 60.656350] Code: 49 8b 02 41 c7 42 18 00 00 00 00 49 c7 42 10 00 00 00 00 83 > > > [ 60.656359] RIP [] blk_rq_map_sg+0x10d/0x17c > > > [ 60.656362] RSP > > > [ 60.656363] CR2: 0000000000000000 > > > > > > Platform is AMD64 and the userspace is Ubuntu 7/10 Gutsy Gibbon. > > I am seeing something similar with 2.6.23-git18 on x86_64 at boot time. > 2.6.23-git16 was working fine. > > > This should fix it, sorry about that. > > > > diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c > > index 61c2e39..de5ba47 100644 > > --- a/block/ll_rw_blk.c > > +++ b/block/ll_rw_blk.c > > @@ -1351,11 +1351,21 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, > > new_segment: > > if (!sg) > > sg = sglist; > > - else > > + else { > > + /* > > + * If the driver previously mapped a shorter > > + * list, we could see a termination bit > > + * prematurely unless it fully inits the sg > > + * table on each mapping. We KNOW that there > > + * must be more entries here or the driver > > + * would be buggy, so force clear the > > + * termination bit to avoid doing a full > > + * sg_init_table() in drivers for each command. > > + */ > > + sg->page_link &= ~0x02; > > sg = sg_next(sg); > > + } > > > > - sg_dma_len(sg) = 0; > > - sg_dma_address(sg) = 0; > > sg_set_page(sg, bvec->bv_page); > > sg->length = nbytes; > > sg->offset = bvec->bv_offset; > > > > > > The patch above indeed fixes the problem for me, as far as I can see. > Thanks Jens! Can you please push this fix to Linus quickly? It's already pushed and pulled, so current git should work again... -- Jens Axboe - 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/