WNDR3800 reboots on mount_root in failsafe mode, can't reset password

[sd1074]

I was trying to reset my forgotten password on WNDR3800 running OpenWRT LEDE (17.01.4, r3560-79f57e422d). Successuflly logged into failsafe mode, however when I try to mount_root, router keeps restarting.

I was able to run logread in failsafe mode after enabling logd and ubus:

ubusd &
logd &

The log shows some crash info, but I can't make much sense out of it. Maybe I can disable some kernel modules? I don't know how to do that though. I would prefer NOT to reset the entire configuration because there was a lot of custom tweaking on this router. Crash log after mount_root:

Thu Jan  1 00:24:22 1970 kern.notice kernel: [ 1462.419472] jffs2: notice: (498) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
Thu Jan  1 00:24:22 1970 user.info kernel: [ 1462.883085] kmodloader: loading kernel modules from /tmp/overlay/upper/etc/modules-boot.d/*
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.091476] Reserved instruction in kernel code[#1]:
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.096449] CPU: 0 PID: 501 Comm: kmodloader Not tainted 4.4.92 #0
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.102617] task: 87d9e338 ti: 8754e000 task.ti: 8754e000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.107997] $ 0   : 00000000 00000000 9a99d527 00000000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.113244] $ 4   : 8767f044 00000001 81102020 00004216
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.118490] $ 8   : 00004215 8755dc00 00000001 00000000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.123737] $12   : 8110217c 00000024 80460000 ffffff80
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.128985] $16   : 00000000 8767f044 803d0000 803e0000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.134232] $20   : 00000000 803e0000 803e0000 80370040
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.139479] $24   : 81102188 00000100                  
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.144726] $28   : 8754e000 8754fd28 00000000 80069c7c
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.149975] Hi    : 001dfeef
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.152850] Lo    : 15320904
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.155733] epc   : 8767f088 0x8767f088 [ext4@87600000+0x4d420]
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.161640] ra    : 80069c7c 0x80069c7c
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.165466] Status: 1000fc03	KERNEL EXL IE 
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.169666] Cause : 10800028 (ExcCode 0a)
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.173667] PrId  : 00019374 (MIPS 24Kc)
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.177578] Modules linked in: ext4(+) jbd2 mbcache crc16 crc32c_generic crypto_hash ohci_platform ohci_hcd ehci_platform ehci_hcd gpio_button_hotplug usbcore nls_base usb_common
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.193568] Process kmodloader (pid: 501, threadinfo=8754e000, task=87d9e338, tls=778f3d48)
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.201892] Stack : 87c51800 800a1d24 00000000 80092ab8 8764cf68 803e0000 00000000 87c51800
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.201892] 	  00000000 800909d8 00000004 87f3700c 87f37000 800904c8 80372670 80441000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.201892] 	  8755d500 00000001 81000000 810eba40 00000001 00000000 00000000 803e0000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.201892] 	  803e0000 9a99d527 00000000 8764cf20 8754fec0 8755d000 803e0000 803e0000
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.201892] 	  803e0000 800c3558 00000001 8764cf2c 8764cf68 800f98fc 8764d04c 8764cf2c
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.201892] 	  ...
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.237636] Call Trace:[<800a1d24>] 0x800a1d24
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.242081] [<80092ab8>] 0x80092ab8
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.245563] [<800909d8>] 0x800909d8
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.249044] [<800904c8>] 0x800904c8
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.252526] [<800c3558>] 0x800c3558
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.256004] [<800f98fc>] 0x800f98fc
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.259486] [<800c4a08>] 0x800c4a08
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.262967] [<800c2bfc>] 0x800c2bfc
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.266450] [<800f9e08>] 0x800f9e08
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.269929] [<800c4c04>] 0x800c4c04
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.273410] [<800c4ca0>] 0x800c4ca0
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.276894] [<80062c6c>] 0x80062c6c
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.280372] [<80065098>] 0x80065098
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.283851] 
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.285336] 
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.285336] Code: 00000000  00000000  00000000 <0000a4ec> 00000000  00000000  00000000  00000000  0000d080 
Thu Jan  1 00:24:23 1970 kern.warn kernel: [ 1463.295379] ---[ end trace e5217913ec5ae9d5 ]---

Any help will be greatly appreciated. Thanks

[slh]

You apparently have ssh access - and all seems to be fine until you invoke mount_root, so the obvious answer would be not to do so. scp the 19.07.7 or 21.02.0-rc3 sysupgrade image to your router's /tmp/, call sysupgrade -n /tmp/openwrt-…-sysupgrade.bin (warning, -n deletes all previous configuration, effectively does a factory reset, which you do want/ need to do here), wait ~5 minutes, /done.

[sd1074]

I was able to reflash, but unfortunately I ended up erasing my old config. Been restoring it for a day already.

[tmomas]

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