Improve freelist walking #12
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libslub got stuck on freelists that contained cycles. Fix by walking no more than `max_objs_per_slab` steps.
fidgetingbits
requested changes
Apr 18, 2025
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Thanks for this. Seems sane aside from the one thing about the hardcoded address. Let me know if you don't have time to fix it and I'll take a stab at it at some point.
Out of curiosity did you run into this bug while exploiting something that corrupted something in the freelist or was it somehow a legitimate state?
| @@ -80,6 +80,9 @@ def to_string(self, name="", verbose=0, use_cache=False, indent=0, colorize_func | |||
| else: | |||
| t = "F" | |||
| address = "{:#x}".format(self.address) | |||
| if self.address < 0xffff800000000000: | |||
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I think we don't currently restrict use of this library to x64 anywhere, so I would say this should be abstracted and per-architecture, otherwise this would break it on anything but x64.
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Hi!
I came across the following situations that libslub couldn´t handle:
For the first one i've added a limit that depends on a maximum capacity of a particular slub. For the second i've added a try-except, and also an explicit check to point non-kernel addresses.
With my fixes it looks like this:
Looking forward to comments/suggestions if you have any. Thanks!