Hi Trond. Anna, On Tue, Dec 5, 2017 at 5:02 PM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > During a failed write to a virtual sysfs file (root fs is NFS), I got: > > Unable to handle kernel NULL pointer dereference at virtual address 00000020 > pgd = c448bb15 > [00000020] *pgd=69c9c003, *pmd=69d55003, *pte=00000000 > Internal error: Oops: 207 [#1] SMP ARM > Modules linked in: > CPU: 0 PID: 1230 Comm: rs:main Q:Reg Not tainted > 4.15.0-rc2-koelsch-01160-gd389a154c640caab-dirty #3752 > Hardware name: Generic R-Car Gen2 (Flattened Device Tree) > task: 4a3bb6d2 task.stack: fd0c00bd > PC is at nfs_flush_incompatible+0x54/0xf8 Got another nfsroot crash: Unable to handle kernel NULL pointer dereference at virtual address 00000030 pgd = 329e8f6e [00000030] *pgd=80000040004003, *pmd=00000000 Internal error: Oops: 206 [#1] SMP ARM Modules linked in: CPU: 0 PID: 101 Comm: kworker/u4:1 Not tainted 4.15.0-rc2-koelsch-01166-g047d7d3248e08fc7-dirty #3762 Hardware name: Generic R-Car Gen2 (Flattened Device Tree) Workqueue: writeback wb_workfn (flush-0:15) task: 8a5bf858 task.stack: e93c92bc PC is at nfs_page_async_flush+0x110/0x244 LR is at 0x10 pc : [<c03bc648>] lr : [<00000010>] psr: 400f0013 sp : eaff9c98 ip : c0c5092b fp : 00000005 r10: 00018e84 r9 : ebef92c0 r8 : eaff9d64 r7 : ea421a00 r6 : ebef92c0 r5 : ea999040 r4 : ea9b1a00 r3 : 00000000 r2 : 00000006 r1 : 00000000 r0 : 00000000 Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 30c5387d Table: 69d65680 DAC: fffffffd Process kworker/u4:1 (pid: 101, stack limit = 0xeaff8210) Stack: (0xeaff9c98 to 0xeaffa000) 9c80: ebef92c0 eaff9d64 9ca0: eaff9e20 ea421afc 00000000 c03bc858 eaff9e20 00000000 ffffffff c02b11e8 9cc0: 00000000 ea8f4500 eb427328 00018e89 00000000 00000009 eaff9d0c 00000000 9ce0: c03bc830 eaff9d64 00000000 ffffffff 00000009 00000000 ebef8440 ebef45c0 9d00: ebf1abc0 ebef8860 ebef8420 ebef92c0 ebef5ce0 ebef7e80 ebef3cc0 eaff9d1c 9d20: eaff9d1c eb1d2d98 eb1d2d28 ea421a00 eb400700 ea421a00 eab89bc0 ea421afc 9d40: eaff9e20 ea421afc 00000002 ea421a50 eaff8000 c03bc94c c081590c c02483d8 9d60: eaa62140 00000001 ea421a00 c08157cc c08158e0 00000000 00000000 c08157bc 9d80: c081590c 00000000 eab89bc0 00000000 00001000 00000001 eaff9d9c ea999fc0 9da0: ea999fc0 00004000 00001000 00001000 00000000 c0745704 00000000 00000000 9dc0: ec09e250 eaff9e20 ea421afc eaff9e20 ea9c4c38 c02b2d48 00000086 ea421a00 9de0: ea421a00 c0310434 ea421a00 eaff9e20 00000000 ea421ab4 ea421a00 00001400 9e00: ea9c4c38 eaff9efc 00000002 c03109b8 ea9c4c64 00003fd0 ea98b800 00000000 9e20: 000013fb 00000000 00000000 00000000 ffffffff 7fffffff 00000000 00000011 9e40: 00000000 ea9c4c38 00000000 c0e04900 00003fda eaff9efc ea9c4c4c ea98b800 9e60: eb1f7584 c0310be0 ea9c4c4c ea9c4c38 eaff9efc c0e04900 ea9c4c64 0000175c 9e80: ea9c4d90 c0e13020 0000000a c0310d2c 00003fd0 00003fd0 eb465198 00003418 9ea0: eaff9ea0 eaff9ea0 eaff9ea8 eaff9ea8 eaff9eb0 eaff9eb0 0000001a ea9c4d98 9ec0: ea9c4c38 0000175c ea9c4d90 ea9c4c3c ea9c4d80 00000000 00000088 c03110a0 9ee0: 00000000 c023b924 eb9a0d80 eafd7100 eb465100 eabe8000 00000000 0000175c 9f00: 00000000 eaff9e9c 00000000 00000006 00000003 00000000 00000000 00000000 9f20: eb7f6200 ea9c4d98 eb406600 00000000 eb407f00 00000000 ea9c4d9c c0235bdc 9f40: eb7f6200 ea9c4d98 eb7f6200 eb406600 eb406600 eaff8000 eb406624 c0e04900 9f60: eb7f6218 c023634c eafd7100 eb7f6380 eb7a7fc0 00000000 eb443ee4 eb7f63a8 9f80: eb7f6200 c0236080 00000000 c023a528 eb7a7fc0 c023a40c 00000000 00000000 9fa0: 00000000 00000000 00000000 c0206f38 00000000 00000000 00000000 00000000 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000 [<c03bc648>] (nfs_page_async_flush) from [<c03bc858>] (nfs_writepages_callback+0x28/0x54) [<c03bc858>] (nfs_writepages_callback) from [<c02b11e8>] (write_cache_pages+0x278/0x364) [<c02b11e8>] (write_cache_pages) from [<c03bc94c>] (nfs_writepages+0xa8/0xe8) [<c03bc94c>] (nfs_writepages) from [<c02b2d48>] (do_writepages+0x34/0x80) [<c02b2d48>] (do_writepages) from [<c0310434>] (__writeback_single_inode+0x34/0x194) [<c0310434>] (__writeback_single_inode) from [<c03109b8>] (writeback_sb_inodes+0x1cc/0x390) [<c03109b8>] (writeback_sb_inodes) from [<c0310be0>] (__writeback_inodes_wb+0x64/0xa0) [<c0310be0>] (__writeback_inodes_wb) from [<c0310d2c>] (wb_writeback+0x110/0x18c) [<c0310d2c>] (wb_writeback) from [<c03110a0>] (wb_workfn+0x1b8/0x304) [<c03110a0>] (wb_workfn) from [<c0235bdc>] (process_one_work+0x1cc/0x31c) [<c0235bdc>] (process_one_work) from [<c023634c>] (worker_thread+0x2cc/0x408) [<c023634c>] (worker_thread) from [<c023a528>] (kthread+0x11c/0x13c) [<c023a528>] (kthread) from [<c0206f38>] (ret_from_fork+0x14/0x3c) Code: e3a02001 e5c32004 ebf98e95 e595300c (e5930030) ---[ end trace 2771b70506a823a3 ]--- static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio, struct page *page) { struct nfs_page *req; int ret = 0; ... /* If there is a fatal error that covers this write, just exit */ if (nfs_error_is_fatal_on_server(req->wb_context->error)) goto out_launder; c03bc644: e595300c ldr r3, [r5, #12] c03bc648: e5930030 ldr r0, [r3, #48] ; 0x30 c03bc64c: ebfffd1b bl c03bbac0 <nfs_error_is_fatal_on_server> req->wb_context must be NULL. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html