From: Marti Raudsepp Subject: NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Date: Wed, 15 Aug 2012 21:33:29 +0300 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: Kernel hackers , ext4 hackers Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Hi list, I was moving and deleting some files between two of my ext4 partitions when it suddenly crashed and dropped me into an kernel oops screen (below). I'm using ext4 on kernel 3.5.1 (Arch Linux). Both likely suspect file systems are stored on LVM2, mounted with data=writeback,errors=remount-ro,noatime EXT4-fs (sda3): mounted filesystem with writeback data mode. Opts: (null) EXT4-fs (dm-1): mounted filesystem with writeback data mode. Opts: errors=remount-ro EXT4-fs (dm-0): mounted filesystem with writeback data mode. Opts: errors=remount-ro I can't be bothered to transcribe all those 64-bit pointer values, but here's the human-readable parts (screen shot links below): BUG: unable to handle kernel NULL pointer dereference at 000...00028 IP: [...] ext4_ext_remove_space+0xaa4/0xef0 [ext4] PGD ... PUD ... PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [... bazillion modules ...] Pid: 3687, comm: rm Tainted: G C 3.5.1-1-ARCH #1 System manufacturer System Product Name/M3A76-CM RIP: 0010:[...] [...] ext4_ext_remove_space [... CPU register dump ...] Process rm (pid: 3687, threadinfo ..., task ...) Call Trace: [...] ext4_ext_truncate+0x183/0x1c0 [ext] [...] ? ext4_mark_inode_dirty+0x7e/0x230 [ext4] [...] ext4_truncate+0x135/0x140 [ext4] [...] ext4_evict_inode+0x40f/0x4e0 [ext4] [...] evict+0xb8/0x1b0 [...] iput+0x105/0x210 [...] do_unlinkat+0x1b/0x50 [...] ? flip_close+0x66/0xa0 [...] sys_unlinkat+0x1b/0x50 [...] system_call_fastpath+0x16/0x1b Code: [...] RIP [...] ext4_ext_remove_space+0xaa4/0xef0 [ext4] CR2: 000...00028 Taint flag C is caused by the staging r8712u driver (Realtek USB Wi-Fi adapter). But I wasn't even using it today, so I doubt that had anything to do with it. Some "screen shots" taken with a webcam (warning: CSI "zoom & enhance" technology required) http://ompldr.org/vZjQ3dw http://ompldr.org/vZjQ3eg http://ompldr.org/vZjQ4MA http://ompldr.org/vZjQ3eQ http://ompldr.org/vZjQ3eA Regards, Marti