Description of problem: I'm very new to GNU/Linux and Fedora, and I'm experimenting with trying to figure out how to change the resolution to Fedora in Hyper-V. I'm also trying to do exact same thing (and apparently have gotten a similar error) on Ubuntu 18.04. I was trying to find out where the resolution for this virtual machine was stored in the hopes of changing it to suit my needs. Thus, on both Fedora and Ubuntu, I ran the following command at the command line: grep -rso 1152x / This is what I ran and on both systems, I got a bug, which I'm reporting both here and to Ubuntu (both are Hyper-V machines). Additional info: reporter: libreport-2.9.5 BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI Modules linked in: nls_utf8 isofs fuse xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun nf_conntrack_netbios_ns nf_conntrack_broadcast xt_CT ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack devlink ip_set nfnetlink ebtable_nat ebtable_broute bridge stp llc ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack libcrc32c iptable_mangle iptable_raw iptable_security ebtable_filter ebtables ip6table_filter ip6_tables sunrpc vfat fat crct10dif_pclmul crc32_pclmul ghash_clmulni_intel intel_rapl_perf hv_utils hv_balloon joydev hv_netvsc hv_storvsc scsi_transport_fc serio_raw hyperv_fb hid_hyperv hyperv_keyboard crc32c_intel hv_vmbus CPU: 0 PID: 49198 Comm: grep Not tainted 4.17.9-200.fc28.x86_64 #1 Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v3.0 03/02/2018 RIP: 0010:read_avail_show+0x18/0x40 [hv_vmbus] RSP: 0018:ffffaa1f84303dc8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffff98b72ce60800 RCX: ffff98b6af7e6550 RDX: 0000000000000000 RSI: ffff98b6f7948000 RDI: ffff98b6f7948000 RBP: ffffffffc0365280 R08: ffff98b6f7948000 R09: ffff98b694e36240 R10: 0000000000000000 R11: 0000000000004000 R12: ffffaa1f84303f08 R13: ffff98b7b934d800 R14: 0000000000000001 R15: ffff98b72ce60800 FS: 00007f709b7a4740(0000) GS:ffff98b6b9000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000004 CR3: 000000017a132005 CR4: 00000000003606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: sysfs_kf_seq_show+0x9f/0x120 seq_read+0x16b/0x460 __vfs_read+0x36/0x170 vfs_read+0x8a/0x140 ksys_read+0x4f/0xb0 do_syscall_64+0x5b/0x160 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f709b055091 RSP: 002b:00007ffeccc6af58 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000008000 RCX: 00007f709b055091 RDX: 0000000000008000 RSI: 000056176477a000 RDI: 0000000000000003 RBP: 0000000000008000 R08: 0000000000000000 R09: 0000000000009008 R10: 0000000000000000 R11: 0000000000000246 R12: 000056176477a000 R13: 0000000000000003 R14: 00005617647797c0 R15: 0000000000000003 Code: 5e 36 c0 0f 46 d0 e8 88 d4 58 f3 48 98 c3 0f 1f 44 00 00 0f 1f 44 00 00 48 8b 87 38 01 00 00 8b 97 48 01 00 00 49 89 f0 4c 89 c7 <8b> 48 04 8b 00 01 c2 89 c6 29 ce 29 ca 39 c1 0f 46 d6 48 c7 c6 RIP: read_avail_show+0x18/0x40 [hv_vmbus] RSP: ffffaa1f84303dc8 CR2: 0000000000000004
Created attachment 1475269 [details] File: dmesg
K.Y., I recall Stephen adding this sysfs interface. It seems we have stale kobjects in some cases.
Stephen just sent a patch, which should be able to fix this: http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2018-August/124965.html
The patch is in 4.19-rc4: commit 6712cc9c22117a8af9f3df272b4a44fd2e4201cd Author: Stephen Hemminger <stephen> Date: Mon Aug 20 21:16:40 2018 +0000 vmbus: don't return values for uninitalized channels For unsupported device types, the vmbus channel ringbuffer is never initialized, and therefore reading the sysfs files will return garbage or cause a kernel OOPS. Fixes: c2e5df616e1a ("vmbus: add per-channel sysfs info") Signed-off-by: Stephen Hemminger <sthemmin> Signed-off-by: K. Y. Srinivasan <kys> Cc: <stable.org> # 4.15 Signed-off-by: Greg Kroah-Hartman <gregkh>
*********** MASS BUG UPDATE ************** We apologize for the inconvenience. There are a large number of bugs to go through and several of them have gone stale. Due to this, we are doing a mass bug update across all of the Fedora 28 kernel bugs. Fedora 28 has now been rebased to 4.20.5-100.fc28. Please test this kernel update (or newer) and let us know if you issue has been resolved or if it is still present with the newer kernel. If you have moved on to Fedora 29, and are still experiencing this issue, please change the version to Fedora 29. If you experience different issues, please open a new bug report for those.
*********** MASS BUG UPDATE ************** This bug is being closed with INSUFFICIENT_DATA as there has not been a response in 3 weeks. If you are still experiencing this issue, please reopen and attach the relevant data from the latest kernel you are running and any data that might have been requested previously.