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Add tests for issue 785 #786

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Add tests for issue 785 #786

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96a9355
Add tests for issue 785
Nov 9, 2024
23bee6f
Merge branch 'vbpf:main' into issue785_repro
Alan-Jowett Nov 12, 2024
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58 changes: 58 additions & 0 deletions test-data/loop.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -463,3 +463,61 @@ messages:
- "1:3: Code is unreachable after 1:3"
- "2 (counter): Loop counter is too large (pc[2] < 100000)"
- "2:3: Code is unreachable after 2:3"

---
# Issue: https://github.com/vbpf/ebpf-verifier/issues/785
# The verifier incorrectly assumes that the loop is infinite.
test-case: Count down loop - incorrectly passes
options: ["termination"]

pre: []

code:
<start>: |
r0 = 0
r1 = 10
<loop>: |
r1 -= 1
if r1 > 1 goto <loop>
exit

post:
- pc[2]=[1, +oo]
- r0.svalue=0
- r0.type=number
- r0.uvalue=0
- r1.svalue=[0, 1]
- r1.type=number
- r1.uvalue=[0, 1]

messages:
- "2: Loop counter is too large (pc[2] < 100000)"

Comment on lines +468 to +495
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🧹 Nitpick (assertive)

Enhance test documentation with more details about the verifier's behavior.

The test case correctly demonstrates the issue where the verifier incorrectly assumes an infinite loop. Consider adding more context in the comments about:

  • Why the verifier incorrectly assumes this is an infinite loop
  • What aspect of the decrementing counter confuses the verifier
  • Expected vs actual behavior of the verifier
 # Issue: https://github.com/vbpf/ebpf-verifier/issues/785
-# The verifier incorrectly assumes that the loop is infinite.
+# The verifier incorrectly assumes that the loop is infinite despite:
+# - Loop having a clear termination condition (r1 > 1)
+# - r1 being decremented from 10 to 1, which should terminate after 9 iterations
+# - No possibility of integer overflow that could cause infinite looping
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
# Issue: https://github.com/vbpf/ebpf-verifier/issues/785
# The verifier incorrectly assumes that the loop is infinite.
test-case: Count down loop - incorrectly passes
options: ["termination"]
pre: []
code:
<start>: |
r0 = 0
r1 = 10
<loop>: |
r1 -= 1
if r1 > 1 goto <loop>
exit
post:
- pc[2]=[1, +oo]
- r0.svalue=0
- r0.type=number
- r0.uvalue=0
- r1.svalue=[0, 1]
- r1.type=number
- r1.uvalue=[0, 1]
messages:
- "2: Loop counter is too large (pc[2] < 100000)"
# Issue: https://github.com/vbpf/ebpf-verifier/issues/785
# The verifier incorrectly assumes that the loop is infinite despite:
# - Loop having a clear termination condition (r1 > 1)
# - r1 being decremented from 10 to 1, which should terminate after 9 iterations
# - No possibility of integer overflow that could cause infinite looping
test-case: Count down loop - incorrectly passes
options: ["termination"]
pre: []
code:
<start>: |
r0 = 0
r1 = 10
<loop>: |
r1 -= 1
if r1 > 1 goto <loop>
exit
post:
- pc[2]=[1, +oo]
- r0.svalue=0
- r0.type=number
- r0.uvalue=0
- r1.svalue=[0, 1]
- r1.type=number
- r1.uvalue=[0, 1]
messages:
- "2: Loop counter is too large (pc[2] < 100000)"

---
test-case: Count up loop
options: ["termination"]

pre: []

code:
<start>: |
r0 = 0
r1 = 0
<loop>: |
r1 += 1
if r1 < 10 goto <loop>
exit

post:
- r0.svalue=0
- r0.type=number
- r0.uvalue=0
- r1.svalue=10
- r1.type=number
- r1.uvalue=10
- r1.svalue=r1.uvalue
- pc[2]=10
- pc[2]=r1.svalue
- pc[2]=r1.uvalue

messages: []
Comment on lines +497 to +523
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🧹 Nitpick (assertive)

Add context about test case's relationship to issue #785.

The test case correctly implements and verifies a counting up loop. Consider adding a comment explaining how this test case relates to issue #785, particularly how it demonstrates the verifier's different behavior with incrementing vs decrementing loops.

 test-case: Count up loop
 options: ["termination"]
+# Complementary test to the count down loop case in issue #785.
+# This demonstrates that the verifier correctly handles incrementing loops,
+# in contrast to its incorrect behavior with decrementing loops.
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
test-case: Count up loop
options: ["termination"]
pre: []
code:
<start>: |
r0 = 0
r1 = 0
<loop>: |
r1 += 1
if r1 < 10 goto <loop>
exit
post:
- r0.svalue=0
- r0.type=number
- r0.uvalue=0
- r1.svalue=10
- r1.type=number
- r1.uvalue=10
- r1.svalue=r1.uvalue
- pc[2]=10
- pc[2]=r1.svalue
- pc[2]=r1.uvalue
messages: []
test-case: Count up loop
options: ["termination"]
# Complementary test to the count down loop case in issue #785.
# This demonstrates that the verifier correctly handles incrementing loops,
# in contrast to its incorrect behavior with decrementing loops.
pre: []
code:
<start>: |
r0 = 0
r1 = 0
<loop>: |
r1 += 1
if r1 < 10 goto <loop>
exit
post:
- r0.svalue=0
- r0.type=number
- r0.uvalue=0
- r1.svalue=10
- r1.type=number
- r1.uvalue=10
- r1.svalue=r1.uvalue
- pc[2]=10
- pc[2]=r1.svalue
- pc[2]=r1.uvalue
messages: []

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