bpf: fix VM out of bounds LoadMemShift check

The bpf VM did not correctly check the bounds of LoadMemShift
instructions, as it used a size of 0 instead of the correct 1.

A LoadMemShift instruction 1 past the end of the input resulted in a
runtime panic:

    panic(0x5c1d40, 0x7cec00)
            /usr/local/go/src/runtime/panic.go:522 +0x1b5
    golang.org/x/net/bpf.loadMemShift(...)
            /home/afabre/go/pkg/mod/golang.org/x/net@v0.0.0-20190603091049-60506f45cf65/bpf/vm_instructions.go:137
    golang.org/x/net/bpf.(*VM).Run(0xc00000ec40, 0xc0000173c8, 0x2, 0x8, 0x2, 0xc0000173c8, 0x0)
            /home/afabre/go/pkg/mod/golang.org/x/net@v0.0.0-20190603091049-60506f45cf65/bpf/vm.go:131 +0xb0a

Fix this, and rework the out of bounds tests for load instructions to:

* Use an offset one past the end of the input, to catch this

* Use a filter that returns 1, to catch cases were the out of bounds
load does not cause a panic, but does not cause the VM to return 0.

Change-Id: I1e68886915207a34f59765805f907f36dc031f70
Reviewed-on: https://go-review.googlesource.com/c/net/+/180979
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
2 files changed
tree: 67b433a70d0cd49a98951675dbcc585e5522ffb1
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. bpf/
  10. codereview.cfg
  11. context/
  12. dict/
  13. dns/
  14. go.mod
  15. go.sum
  16. html/
  17. http/
  18. http2/
  19. icmp/
  20. idna/
  21. internal/
  22. ipv4/
  23. ipv6/
  24. lif/
  25. nettest/
  26. netutil/
  27. proxy/
  28. publicsuffix/
  29. route/
  30. trace/
  31. webdav/
  32. websocket/
  33. xsrftoken/
README.md

Go Networking

This repository holds supplementary Go networking libraries.

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The easiest way to install is to run go get -u golang.org/x/net. You can also manually git clone the repository to $GOPATH/src/golang.org/x/net.

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