(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Fri, 08 Jun 2018 16:25:31 +0000 bugzilla-daemon@bugzilla.kernel.org wrote:

> https://bugzilla.kernel.org/show_bug.cgi?id=199999
> 
>             Bug ID: 199999
>            Summary: memremap attempted on mixed range  lockup.
>            Product: Memory Management
>            Version: 2.5
>     Kernel Version: 4.14.48
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>           Assignee: akpm@linux-foundation.org
>           Reporter: me@hussam.eu.org
>         Regression: No

That WARN_ON in memremap() (soon perhaps devm_memremap_pages()) is
triggering on /dev/mem.

> hello. I was poking around and for no real reason, I did cat /dev/mem and
> strings /dev/mem.
> Then I saw the following warning in dmesg. I saved it and rebooted
> immediately.
> 
> Jun 08 19:07:25 hades kernel: memremap attempted on mixed range
> 0x000000000009c000 size: 0x1000
> Jun 08 19:07:25 hades kernel: ------------[ cut here ]------------
> Jun 08 19:07:25 hades kernel: WARNING: CPU: 0 PID: 11810 at
> kernel/memremap.c:98 memremap+0x104/0x170
> Jun 08 19:07:25 hades kernel: Modules linked in: button isofs udf crc_itu_t
> loop nls_iso8859_1 nls_cp437 vfat fat uas usb_storage fuse bsd_comp
> ipt_MASQUERADE nf_nat_masquerade_ipv4 act_police sch_ingress cls_u32 sch_sfq
> iptable_nat nf_c>
> Jun 08 19:07:25 hades kernel:  thermal snd_pcm snd_timer snd video soundcore
> shpchp mei_me mei fan i2c_i801 acpi_pad sch_fq_codel nvidia_uvm(PO)
> nvidia(PO)
> ipmi_devintf ipmi_msghandler nbd crypto_user ip_tables x_tables ext4
> crc32c_gener>
> Jun 08 19:07:25 hades kernel: CPU: 0 PID: 11810 Comm: strings Tainted: P      
>    O    4.14.48-1-lts #1
> Jun 08 19:07:25 hades kernel: Hardware name: LENOVO 90DA00D7AD/SKYBAY, BIOS
> FYKT58A 06/02/2016
> Jun 08 19:07:25 hades kernel: task: ffff9393c0be3b00 task.stack:
> ffffb41287a3c000
> Jun 08 19:07:25 hades kernel: RIP: 0010:memremap+0x104/0x170
> Jun 08 19:07:25 hades kernel: RSP: 0018:ffffb41287a3fdc8 EFLAGS: 00010282
> Jun 08 19:07:25 hades kernel: RAX: 0000000000000041 RBX: 0000000000000000
> RCX:
> 0000000000000000
> Jun 08 19:07:25 hades kernel: RDX: 0000000000000000 RSI: ffff9396bec165d8
> RDI:
> ffff9396bec165d8
> Jun 08 19:07:25 hades kernel: RBP: 0000000000000001 R08: 0000000000000412
> R09:
> 0000000000000004
> Jun 08 19:07:25 hades kernel: R10: 0000000000000000 R11: 0000000000000001
> R12:
> 0000000000001000
> Jun 08 19:07:25 hades kernel: R13: 000055630d83b020 R14: ffff9396a5ec3000
> R15:
> 0000000000000000
> Jun 08 19:07:25 hades kernel: FS:  00007fa2611ddb80(0000)
> GS:ffff9396bec00000(0000) knlGS:0000000000000000
> Jun 08 19:07:25 hades kernel: CS:  0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033
> Jun 08 19:07:25 hades kernel: CR2: 000055630d83c028 CR3: 00000001d5388006
> CR4:
> 00000000003606f0
> Jun 08 19:07:25 hades kernel: Call Trace:
> Jun 08 19:07:25 hades kernel:  xlate_dev_mem_ptr+0x25/0x40
> Jun 08 19:07:25 hades kernel:  read_mem+0x89/0x1a0
> Jun 08 19:07:25 hades kernel:  __vfs_read+0x36/0x170
> Jun 08 19:07:25 hades kernel:  ? __fsnotify_parent+0x91/0x120
> Jun 08 19:07:25 hades kernel:  vfs_read+0x89/0x130
> Jun 08 19:07:25 hades kernel:  SyS_read+0x52/0xc0
> Jun 08 19:07:25 hades kernel:  do_syscall_64+0x67/0x120
> Jun 08 19:07:25 hades kernel:  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> Jun 08 19:07:25 hades kernel: RIP: 0033:0x7fa2609fd4a1
> Jun 08 19:07:25 hades kernel: RSP: 002b:00007ffef180bb58 EFLAGS: 00000246
> ORIG_RAX: 0000000000000000
> Jun 08 19:07:25 hades kernel: RAX: ffffffffffffffda RBX: 000055630d818470
> RCX:
> 00007fa2609fd4a1
> Jun 08 19:07:25 hades kernel: RDX: 0000000000001000 RSI: 000055630d83b020
> RDI:
> 0000000000000003
> Jun 08 19:07:25 hades kernel: RBP: 0000000000000d68 R08: 0000000000000000
> R09:
> 0000000000000004
> Jun 08 19:07:25 hades kernel: R10: 0000000000000000 R11: 0000000000000246
> R12:
> 00007fa260c94720
> Jun 08 19:07:25 hades kernel: R13: 00007fa260c95260 R14: 00007ffef180bc14
> R15:
> 00007ffef180bc08
> Jun 08 19:07:25 hades kernel: Code: 48 83 c4 08 5b 5d 41 5c c3 80 3d 18 de f5
> 00 00 75 b7 4c 89 e2 48 89 e6 48 c7 c7 e8 db df 90 c6 05 02 de f5 00 01 e8 07
> fa f4 ff <0f> 0b eb 9a 4c 89 e6 48 89 df e8 0d f8 ed ff 48 85 c0 74 99 48 
> Jun 08 19:07:25 hades kernel: ---[ end trace 5bdcf881c57b4daa ]---
> 
> -- 
> You are receiving this mail because:
> You are the assignee for the bug.

On Fri, 2018-06-08 at 20:55 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> That WARN_ON in memremap() (soon perhaps devm_memremap_pages()) is
> triggering on /dev/mem.

Hi. Just so I understand correctly, is this expected or is it a bug?

(In reply to Hussam Al-Tayeb from comment #2)
> On Fri, 2018-06-08 at 20:55 +0000, bugzilla-daemon@bugzilla.kernel.org
> wrote:
> > That WARN_ON in memremap() (soon perhaps devm_memremap_pages()) is
> > triggering on /dev/mem.
> 
> Hi. Just so I understand correctly, is this expected or is it a bug?

It's a bug. Here's the fix:

    https://patchwork.kernel.org/patch/10456221/


...thanks for the report.

On Sun, 2018-06-10 at 16:19 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> It's a bug. Here's the fix:
> 
>     https://patchwork.kernel.org/patch/10456221/
> 
> 
> ...thanks for the report.
> 

Thank you. I saw the mail yesterday and applied the patch on top of
4.14.48 and it fixed the bug. Thank you very much for the quick fix.

@Dan, I am using this patch (re-diffed) on top of 4.14.49 and I haven't noticed any regressions so far. Do I need additional patches or does this one suffice?
Thank you again.

(In reply to Hussam Al-Tayeb from comment #5)
> @Dan, I am using this patch (re-diffed) on top of 4.14.49 and I haven't
> noticed any regressions so far. Do I need additional patches or does this
> one suffice?

Should be good to go with that one... and it will be backported to the 4.14 series in the coming days. So you should be able to stop applying it manually in the next 1 to 2 4.14-stable releases.

They merged the patch in 4.14.53