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When I insert a USB, macOS system (running High Sierra, Mavericks, Mojave) restarts or freezes with a panic report:

Panic Report:

panic(cpu 0 caller 0xffffff801e4ba207): "a freed zone element has been modified in zone kalloc.16: 
expected 0x3f0011b64302a888 but found 0x3f0011b64302a800, bits changed 0x88, at offset 0 of 16 in element 0xffffff8030ed5ac0, 
cookies 0x3f0011b64302a888 0x5352105058b7571"
@/BuildRoot/Library/Caches/com.apple.xbs/Sources/xnu/xnu-4570.71.2/osfmk/kern/zalloc.c:1122

What exactly does "a freed zone element has been modified in zone kalloc.16" mean and how we get it resolved?

the kernel is getting panic when I am using a third party kernel extension to which I have modified and that deals with USB control. could you please suggest me any of debugging method of kext too.

marked as duplicate by Graham Miln, Nimesh Neema, Ɱark Ƭ, IconDaemon, fsb Apr 23 at 13:30

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  • Explaining what a kernel panic is far too broad for an answer here without some very specific assumptions on experience level. Why not focus on how to triage / resolve this? One question per question is best practice here. – bmike Apr 23 at 8:31
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    See What is a Kernel Panic and what does it mean? for a useful starting point. – Graham Miln Apr 23 at 8:46
  • @bmike i am using a third party extension that can be a cause to system panic but i am not figuring out this panic is because of the memory or not as reported in panic report,for debugging this issue i use two machine debugging method but still not get any clue – bhardwaj_himanshu Apr 23 at 10:22
  • @bhardwaj_himanshu - might be helpful to illustrate what's going on w/ the freed zone bit - objective-see.com/blog/blog_0x1C.html – slm Apr 23 at 12:28
  • Because this question is marked as a duplicate (which is questionable as the duplicate is very broad) - I cannot provide you with the answer as a real answer unfortunately. However, I can in short terms describe the meaning of the kernel panic for you here in a comment: Basically the operating system kernel manages the memory (RAM) in the computer in order to ensure that two seperate tasks do not use the same piece of memory, which would lead to bugs. For memory used internally by the kernel, it does this by managing a number of zones. A zone is simply a block of memory that the kernel (cont) – jksoegaard Apr 23 at 14:13

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