Big Sur panic when connect/disconnect usb-c dock

I have been encountering this issue for like 3 months already. It's good to see a dedicated thread for this but too bad it's still an issue and we're already in page 7. I am using my 2019 Macbook Pro 16" at Big Sur 11.5

panic(cpu 2 caller 0xffffff801749a9b6): [kext.kalloc.2048]: element modified after free (off:1672, val:0xfffffffe00000000, sz:2048, ptr:0xffffff9373558000, prot:zero)
1672: 0xfffffffe00000000
Backtrace (CPU 2), Frame : Return Address
0xffffffb0e5f4a550 : 0xffffff8016c8915d 
0xffffffb0e5f4a5a0 : 0xffffff8016dd0033 
0xffffffb0e5f4a5e0 : 0xffffff8016dc062a 
0xffffffb0e5f4a630 : 0xffffff8016c2da2f 
0xffffffb0e5f4a650 : 0xffffff8016c8897d 
0xffffffb0e5f4a770 : 0xffffff8016c88c73 
0xffffffb0e5f4a7e0 : 0xffffff801749898a 
0xffffffb0e5f4a850 : 0xffffff801749a9b6 
0xffffffb0e5f4acd0 : 0xffffff8016ce7b56 
0xffffffb0e5f4ad40 : 0xffffff8016c9873c 
0xffffffb0e5f4ad90 : 0xffffff80173a95f2 
0xffffffb0e5f4adb0 : 0xffffff8019d5a41c 
0xffffffb0e5f4add0 : 0xffffff8019d683fc 
0xffffffb0e5f4ae30 : 0xffffff8019d5ab6e 
0xffffffb0e5f4aed0 : 0xffffff8019d5cce7 
0xffffffb0e5f4b180 : 0xffffff8019d60b7d 
0xffffffb0e5f4b450 : 0xffffff8019d7023f 
0xffffffb0e5f4b640 : 0xffffff8019d560b4 
0xffffffb0e5f4b9e0 : 0xffffff8019d56abf 
0xffffffb0e5f4ba40 : 0xffffff801747c4a6 
0xffffffb0e5f4ba80 : 0xffffff8016f5144e 
0xffffffb0e5f4bd50 : 0xffffff8016f32e43 
0xffffffb0e5f4bf40 : 0xffffff801733ad9e 
0xffffffb0e5f4bfa0 : 0xffffff8016c2e1f6 
      Kernel Extensions in backtrace:
         com.apple.security.sandbox(300.0)[1D016FA0-09CF-3D63-A613-57B7A8AA640C]@0xffffff8019d49000->0xffffff8019d8efff
            dependency: com.apple.driver.AppleMobileFileIntegrity(1.0.5)[F5BC1EC5-40C5-36E6-8F25-BA1DFE57654A]@0xffffff80182c0000->0xffffff80182d5fff
            dependency: com.apple.iokit.IOStorageFamily(2.1)[3DE94082-367D-3255-9BE7-7F5A87838247]@0xffffff801986e000->0xffffff801987ffff
            dependency: com.apple.kext.AppleMatch(1.0.0d1)[87BEAD84-D39B-36F5-9703-26D5D48C188D]@0xffffff80182bc000->0xffffff80182befff

Process name corresponding to current thread: NotificationCenter
Boot args: chunklist-security-epoch=0 -chunklist-no-rev2-dev chunklist-security-epoch=0 -chunklist-no-rev2-dev

Mac OS version:
20G5023d

Kernel version:
Darwin Kernel Version 20.6.0: Mon May 10 03:15:35 PDT 2021; root:xnu-7195.140.13.0.1~20/RELEASE_X86_64
Kernel UUID: 3893CD5D-E480-3097-A4F4-3F1A6D146AE4
KernelCache slide: 0x0000000016a00000
KernelCache base:  0xffffff8016c00000
Kernel slide:      0x0000000016a10000
Kernel text base:  0xffffff8016c10000
__HIB  text base: 0xffffff8016b00000
System model name: MacBookPro16,1 (Mac-E1008331FDC96864)
System shutdown begun: NO
Hibernation exit count: 11

Been having this issue at work for about 3 months now. It had gotten worse and worse. Every update that comes out i install instantly but it only makes the crashed happen more frequent. I'm really regetting updating to Big Sur.

The following crash will happen about 2 times a day. It's always when i connect one of my external monitors usb-c to display.

panic(cpu 10 caller 0xffffff801b69fc36): [kext.kalloc.2048]: element modified after free (off:1672, val:0xfffffffe00000000, sz:2048, ptr:0xffffff93787f5800, prot:zero)
 1672: 0xfffffffe00000000
Backtrace (CPU 10), Frame : Return Address
0xffffffb0e4842cf0 : 0xffffff801ae8e04d 
0xffffffb0e4842d40 : 0xffffff801afd4e13 
0xffffffb0e4842d80 : 0xffffff801afc540a 
0xffffffb0e4842dd0 : 0xffffff801ae32a2f 
0xffffffb0e4842df0 : 0xffffff801ae8d86d 
0xffffffb0e4842f10 : 0xffffff801ae8db63 
0xffffffb0e4842f80 : 0xffffff801b69dc0a 
0xffffffb0e4842ff0 : 0xffffff801b69fc36 
0xffffffb0e4843470 : 0xffffff801aeec9e6 
0xffffffb0e48434e0 : 0xffffff801ae9d65c 
0xffffffb0e4843530 : 0xffffff801b5ae872 
0xffffffb0e4843550 : 0xffffff7fb52fefce 
0xffffffb0e4843600 : 0xffffff7fb52ff65e 
0xffffffb0e4843640 : 0xffffff7fb52bfc4a 
0xffffffb0e4843660 : 0xffffff7fb5bf9e78 
0xffffffb0e4843900 : 0xffffff7fb52c07e8 
0xffffffb0e4843930 : 0xffffff7fb5bfb074 
0xffffffb0e48439c0 : 0xffffff7fb5bf90f7 
0xffffffb0e4843a10 : 0xffffff7fb5bf8ee7 
0xffffffb0e4843a60 : 0xffffff7fb5bf7f99 
0xffffffb0e4843aa0 : 0xffffff801b61e4be 
0xffffffb0e4843af0 : 0xffffff7fb52c04a6 
0xffffffb0e4843b20 : 0xffffff801b62876b 
0xffffffb0e4843c80 : 0xffffff801af80841 
0xffffffb0e4843d90 : 0xffffff801ae936cd 
0xffffffb0e4843e00 : 0xffffff801ae69cf5 
0xffffffb0e4843e60 : 0xffffff801ae81252 
0xffffffb0e4843ef0 : 0xffffff801afa970d 
0xffffffb0e4843fa0 : 0xffffff801ae33216 
      Kernel Extensions in backtrace:
         com.apple.iokit.IOAcceleratorFamily2(442.9)[8F6B0D56-AFD7-38F7-8EDA-B43ACA468394]@0xffffff7fb5bb4000->0xffffff7fb5c1efff
            dependency: com.apple.driver.AppleMobileFileIntegrity(1.0.5)[152D7047-0D43-3CA8-B1EA-251D3F80AC28]@0xffffff801c4c0000->0xffffff801c4d5fff
            dependency: com.apple.iokit.IOGraphicsFamily(585.1)[B5241FDE-C525-39D6-9813-2BE73DD7CEE3]@0xffffff7fb5d35000->0xffffff7fb5d63fff
            dependency: com.apple.iokit.IOPCIFamily(2.9)[F7AA4BAF-35CF-3784-A50C-5FD9CDCBE488]@0xffffff801d96c000->0xffffff801d994fff
            dependency: com.apple.iokit.IOReportFamily(47)[AE367C5D-FEFC-390D-ABDF-86E037890F00]@0xffffff801d9a3000->0xffffff801d9a5fff
            dependency: com.apple.iokit.IOSurface(290.8.1)[DCE8209F-A72D-3EBA-BE93-C0AF896AA9B5]@0xffffff801da96000->0xffffff801dab2fff
         com.apple.driver.AppleIntelKBLGraphics(16.0.5)[8B11EE30-3D67-3FB9-9F2E-46A1B159E059]@0xffffff7fb52a9000->0xffffff7fb5360fff
            dependency: com.apple.iokit.IOAcceleratorFamily2(442.9)[8F6B0D56-AFD7-38F7-8EDA-B43ACA468394]@0xffffff7fb5bb4000->0xffffff7fb5c1efff
            dependency: com.apple.iokit.IOGraphicsFamily(585.1)[B5241FDE-C525-39D6-9813-2BE73DD7CEE3]@0xffffff7fb5d35000->0xffffff7fb5d63fff
            dependency: com.apple.iokit.IOPCIFamily(2.9)[F7AA4BAF-35CF-3784-A50C-5FD9CDCBE488]@0xffffff801d96c000->0xffffff801d994fff
            dependency: com.apple.iokit.IOSurface(290.8.1)[DCE8209F-A72D-3EBA-BE93-C0AF896AA9B5]@0xffffff801da96000->0xffffff801dab2fff

Process name corresponding to current thread: TouchBarServer
Boot args: chunklist-security-epoch=0 -chunklist-no-rev2-dev

Mac OS version:
20G80

Kernel version:
Darwin Kernel Version 20.6.0: Wed Jun 23 00:26:31 PDT 2021; root:xnu-7195.141.2~5/RELEASE_X86_64
Kernel UUID: FECBF22B-FBBE-36DE-9664-F12A7DD41D3D
KernelCache slide: 0x000000001ac00000
KernelCache base:  0xffffff801ae00000
Kernel slide:      0x000000001ac10000
Kernel text base:  0xffffff801ae10000
__HIB  text base: 0xffffff801ad00000
System model name: MacBookPro16,1 (Mac-E1008331FDC96864)
System shutdown begun: NO
Hibernation exit count: 1

Happens to me as well as described by @dbdotconf. I use 2 monitors with 16'' 2021 Big Sur 11.5.1. The same flow of actions, almost every day when I plug in monitors via 2 TB3, I hear fans and then it crashes and reboots. Also send report every time. This is very annoying. Such amount of money was paid not for such an experience with Mac which is supposed to be ideal.

And yes my crash starts with "[kext.kalloc.2048]: element modified after free" and cpu panic as well.

cpu...panic...[kext.kalloc.2048]: element modified after free....

2021 16'' Big Sur 11.5.1, still happens every day when I start my work in the morning and connect 2 monitors via TB3.

Jeeezzzz...

After reading the thread, I saw someone mentioned that the issue could probably occur when connecting the usb-c dock while the laptop is on sleep.

Since yesterday, I open the lid of my macbook and wait for it to wakeup before I connect the cable. I only do this when my macbook is on sleep, usually every morning. I have not encountered the problem again. Hopefully...

Can anyone confirm if issue is fixed with 11.5.2? Only working solution for me is as commented before, disconnect open the lid wait for laptop to wake up and then reconnect.

I confirm that  kjbalgos's trick is helping to some extent; not 100% safe in my case, but definitely better; thanks !

I was constantly running into this problem. Problem went away completely after I switched to a thunderbolt 4 dock, specifically this one - https://www.caldigit.com/thunderbolt-4-element-hub/

i'm having the same problems - crashes when disconnecting from docking station / external displays, crashing when trying to come out of sleep mode, etc. crash report is attached.

[MacBook Pro (16-inch, 2019) / 2.6 GHz 6-Core Intel Core i7 / 16 GB 2667 MHz DDR4 / Intel UHD Graphics 630 1536 MB]

The problem does not seem to be tied to any particular dock. I have none of those, but every morning I get that panic. My usual use case: work unplugged, close the lid, plug in a charger. If I open the lid while plugged, it never happens. But if I unplug first, then it most likely shoots. Though the bug it not stable, too. My usual case does not trigger it throughout a day — next day only in most cases... MBP16.2

Yes, I have the exact problem..

I don't even use a USB Dock, I have to USB-C Screens with regular USB 3 ports on them. But still.. This is getting so frustrating almost used it a year now and I'm seriously thinking of going back to the dark side....

Does @apple even care about this?

If you think you can fly, you don't

I have 3 different MacBook Pros on Big Sur 11.5.2 that I connect to the same docking station, obviously one MBP at the time, only one presents this problem the main difference is that the one that crashes every time has a 'AMD Radeon Pro 5500M 8 GB' graphics card, whereas the other ones don't only the 'Intel Iris Plus Graphics'.

Surprisingly the one that presents the problem is my most powerful and newest one. MacBook Pro (16-inch, 2019) 2.4 GHz 8-Core Intel Core i9 64 GB 2667 MHz DDR4 AMD Radeon Pro 5500M 8 GB Intel UHD Graphics 630 1536 MB

I'm planning to upgrade the docking station with the hopes that a new one fixes the problem, but Apple should fix ASAP for us

Has anyone tried upgrading to 11.6 yet?

MacOS Big Sur 11.5.2 and I am still seeing the issue. After the 5th crash today it managed to connect to the external monitor (using dell docking station)

Have disconnected and reconnected a few times now with MacOS Big Sur 11.6 and so far so good. I was able to reproduce fairly consistently before.

Has anyone else reproduced this issue on 11.6?

mcbp 16 '19 (Big Sur 11.5.2) Same issue here, tried with HP docs and DELL dock. Please fix this. Occurs even with hdmi not only dp. Every time I connect the usb-c dock the device switch to 2-monitor view (the desktop on the laptop change so I know it's connected in double monitor config.) and I see nothing on the second monitor connected tot he dock. after 1 minute max, fan spins, mac crashes an reboots. I tried multiple times sometimes it works after 10-15 attempts, but I'm scared to damage the device so I reverted back to no dock. Please fix this.

I'm getting the exact same issue on my 2019 16" intel MBP

This is with a HP Usb-C gen5 dock. Sometimes the display works but it only detects 60Hz. Other times it forces the mac to shutdown.

Most times when you plug it in and the screen doesnt show, the mac freezes every few seconds.

on my M1 air the dock/screen works fine.

When running bootcamp on the 2019 !6" MBP the dock/screen works fine too.

Care to chime in @Apple? This bug is costing me hours a week on a brand new $3k MacBook Pro. I thought things were supposed to "just work"...including the basics such as connecting an external display.

Hello, Same problem with my Macbook pro 2019 (with AMD 5300).

Updated on Big sur 11.6.

Tried with different adapters. If I plug/unplug one of them or both -> Kernel Panic almost each time.

After two calls with Apple care team, they told me to "reinstall macOs Big Sur". Without any changes...

So, I just lost a day of work to try to avoid the case. With no solution...

Same problem - multiple crashes per day. Crashes often occur in display driver (com.apple.kext.AMDRadeonX6000Framebuffer), but not always.

How is it possible to have less stable drivers on mac than on windows, when windows has to support 1000s of hardware configurations? This is embarrassing.

Having the same issue reboot due to Kernel panic 🤬🤬🤬 apple support just recommended reinstall OS 🤦‍♂️

MacBook Pro (16-inch, 2019) current MacOS Big Sur 11.6 (the issue still observed) Dell Thunderbolt Dock WD19TB

panic(cpu 4 caller 0xffffff800b89fc36): [kext.kalloc.2048]: element modified after free (off:1672, val:0xffffffff00000000, sz:2048, ptr:0xffffff9383b7f000, prot:zero)  1672: 0xffffffff00000000

I am having the same issue using a Dock station Lenovo Thinkpad after the upgrade to the BigSur version.

panic(cpu 8 caller 0xffffff8004c9edf6): [kext.kalloc.2048]: element modified after free (off:1672, val:0xfffffffe00000000, sz:2048, ptr:0xffffff9361e6d000, prot:zero)
 1672: 0xfffffffe00000000
Backtrace (CPU 8), Frame : Return Address
0xffffffb0cdc9acf0 : 0xffffff800448cfdd 
0xffffffb0cdc9ad40 : 0xffffff80045d3fd3 
0xffffffb0cdc9ad80 : 0xffffff80045c45ca 
0xffffffb0cdc9add0 : 0xffffff8004431a2f 
0xffffffb0cdc9adf0 : 0xffffff800448c7fd 
0xffffffb0cdc9af10 : 0xffffff800448caf3 
0xffffffb0cdc9af80 : 0xffffff8004c9cdca 
0xffffffb0cdc9aff0 : 0xffffff8004c9edf6 
0xffffffb0cdc9b470 : 0xffffff80044eb976 
0xffffffb0cdc9b4e0 : 0xffffff800449c5ec 
0xffffffb0cdc9b530 : 0xffffff8004bada32 
0xffffffb0cdc9b550 : 0xffffff7f9e8fefe2 
0xffffffb0cdc9b600 : 0xffffff7f9e8ff672 
0xffffffb0cdc9b640 : 0xffffff7f9e8bfc62 
0xffffffb0cdc9b660 : 0xffffff7f9f1f9e78 
0xffffffb0cdc9b900 : 0xffffff7f9e8c0800 
0xffffffb0cdc9b930 : 0xffffff7f9f1fb074 
0xffffffb0cdc9b9c0 : 0xffffff7f9f1f90f7 
0xffffffb0cdc9ba10 : 0xffffff7f9f1f8ee7 
0xffffffb0cdc9ba60 : 0xffffff7f9f1f7f99 
0xffffffb0cdc9baa0 : 0xffffff8004c1d67e 
0xffffffb0cdc9baf0 : 0xffffff7f9e8c04be 
0xffffffb0cdc9bb20 : 0xffffff8004c2792b 
0xffffffb0cdc9bc80 : 0xffffff800457f7d1 
0xffffffb0cdc9bd90 : 0xffffff800449265d 
0xffffffb0cdc9be00 : 0xffffff8004468cd5 
0xffffffb0cdc9be60 : 0xffffff80044801e2 
0xffffffb0cdc9bef0 : 0xffffff80045a869d 
0xffffffb0cdc9bfa0 : 0xffffff8004432216 
      Kernel Extensions in backtrace:

Same issue here. Happens around 5-10 times a month when I connect external Dell U2719DC monitor via USB C:

panic(cpu 2 caller 0xffffff801669edf6): [kext.kalloc.2048]: element modified after free (off:1672, val:0xfffffffe00000000, sz:2048, ptr:0xffffff937592b800, prot:zero)
 1672: 0xfffffffe00000000
Backtrace (CPU 2), Frame : Return Address
0xffffffa0e2052cf0 : 0xffffff8015e8cfdd 
0xffffffa0e2052d40 : 0xffffff8015fd3fd3 
0xffffffa0e2052d80 : 0xffffff8015fc45ca 
0xffffffa0e2052dd0 : 0xffffff8015e31a2f 
0xffffffa0e2052df0 : 0xffffff8015e8c7fd 
0xffffffa0e2052f10 : 0xffffff8015e8caf3 
0xffffffa0e2052f80 : 0xffffff801669cdca 
0xffffffa0e2052ff0 : 0xffffff801669edf6 
0xffffffa0e2053470 : 0xffffff8015eeb976 
0xffffffa0e20534e0 : 0xffffff8015e9c5ec 
0xffffffa0e2053530 : 0xffffff80165ada32 
0xffffffa0e2053550 : 0xffffff7fb02fefe2 
0xffffffa0e2053600 : 0xffffff7fb02ff672 
0xffffffa0e2053640 : 0xffffff7fb02bfc62 
0xffffffa0e2053660 : 0xffffff7fb0bf9e78 
0xffffffa0e2053900 : 0xffffff7fb02c0800 
0xffffffa0e2053930 : 0xffffff7fb0bfb074 
0xffffffa0e20539c0 : 0xffffff7fb0bf90f7 
0xffffffa0e2053a10 : 0xffffff7fb0bf8ee7 
0xffffffa0e2053a60 : 0xffffff7fb0bf7f99 
0xffffffa0e2053aa0 : 0xffffff801661d67e 
0xffffffa0e2053af0 : 0xffffff7fb02c04be 
0xffffffa0e2053b20 : 0xffffff801662792b 
0xffffffa0e2053c80 : 0xffffff8015f7f7d1 
0xffffffa0e2053d90 : 0xffffff8015e9265d 
0xffffffa0e2053e00 : 0xffffff8015e68cd5 
0xffffffa0e2053e60 : 0xffffff8015e801e2 
0xffffffa0e2053ef0 : 0xffffff8015fa869d 
0xffffffa0e2053fa0 : 0xffffff8015e32216 
      Kernel Extensions in backtrace:
         com.apple.iokit.IOAcceleratorFamily2(442.9)[065DAA9E-DE99-3C6D-A8D6-06BFD26CA1DC]@0xffffff7fb0bb4000->0xffffff7fb0c1efff
            dependency: com.apple.driver.AppleMobileFileIntegrity(1.0.5)[A994AEFE-3919-310E-A2C9-405E864BCB7B]@0xffffff80174c0000->0xffffff80174d5fff
            dependency: com.apple.iokit.IOGraphicsFamily(585.1)[240F08CD-4BC4-3093-8832-0E899EFC14F4]@0xffffff7fb0d35000->0xffffff7fb0d63fff
            dependency: com.apple.iokit.IOPCIFamily(2.9)[4E85D41F-6AD7-3C24-911C-A8B80B599F86]@0xffffff801896c000->0xffffff8018994fff
            dependency: com.apple.iokit.IOReportFamily(47)[77F098F2-012A-32EF-BD19-8A0E7ADF46E9]@0xffffff80189a3000->0xffffff80189a5fff
            dependency: com.apple.iokit.IOSurface(290.8.1)[3BE6ED95-B932-3F71-9DD5-4563CF4BD0DC]@0xffffff8018a96000->0xffffff8018ab2fff
         com.apple.driver.AppleIntelKBLGraphics(16.0.5)[493FBA7F-5361-30A7-9A49-57162C8351AD]@0xffffff7fb02a9000->0xffffff7fb0360fff
            dependency: com.apple.iokit.IOAcceleratorFamily2(442.9)[065DAA9E-DE99-3C6D-A8D6-06BFD26CA1DC]@0xffffff7fb0bb4000->0xffffff7fb0c1efff
            dependency: com.apple.iokit.IOGraphicsFamily(585.1)[240F08CD-4BC4-3093-8832-0E899EFC14F4]@0xffffff7fb0d35000->0xffffff7fb0d63fff
            dependency: com.apple.iokit.IOPCIFamily(2.9)[4E85D41F-6AD7-3C24-911C-A8B80B599F86]@0xffffff801896c000->0xffffff8018994fff
            dependency: com.apple.iokit.IOSurface(290.8.1)[3BE6ED95-B932-3F71-9DD5-4563CF4BD0DC]@0xffffff8018a96000->0xffffff8018ab2fff

Process name corresponding to current thread: WindowServer
Boot args: chunklist-security-epoch=0 -chunklist-no-rev2-dev chunklist-security-epoch=0 -chunklist-no-rev2-dev

Mac OS version:
20G165

Kernel version:
Darwin Kernel Version 20.6.0: Mon Aug 30 06:12:21 PDT 2021; root:xnu-7195.141.6~3/RELEASE_X86_64

Lo and behold. Disabling DisplayPort 1.2 in my monitor solved the issue for me. This was suggested as a fix by others in comments to earlier messages. I used to have consistent crashes once or twice per day, typically shortly after powering on the monitor. I disabled DisplayPort 1.2 five days ago and have not had a single crash since.

My specs for those interested:

• MacBook Pro (16-inch, 2019) with AMD Radeon Pro 5500M 4 GB
• Monitor: Dell U3014 30", connected with USB-C to DisplayPort cable (no hubs or adapters)