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Bufferoverrun Analysis - small fixes and improvements #1736

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Bufferoverrun Analysis - small fixes and improvements #1736

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31ab607
[inferbo] Fix an ignored case when the upper bounds of offset is +oo,…
sjxer723 Feb 3, 2023
fd0a4e6
[inferbo] Make a more precise upper/lower bound when adding two upper…
sjxer723 Feb 6, 2023
347d391
[inferbo] Initialize locations for arrays within struct typed variables
sjxer723 Feb 24, 2023
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4 changes: 4 additions & 0 deletions infer/src/bufferoverrun/bufferOverrunProofObligations.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -347,6 +347,10 @@ module ArrayAccessCondition = struct
Bound.is_not_infty (ItvPure.ub real_idx) && Bound.le (ItvPure.ub size) (ItvPure.ub real_idx)
then {report_issue_type= Issue IssueType.buffer_overrun_l2; propagate= false}
(* symbolic il >= sl, probably an error *)
else if
Bound.is_infty (ItvPure.ub real_idx) && Bound.is_not_infty (ItvPure.ub size)
then {report_issue_type= Issue IssueType.buffer_overrun_l3; propagate= false}
(* su < iu = +oo, probably an error *)
Comment on lines +350 to +353
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@skcho skcho Feb 28, 2023 •
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However, this error was missed by buffer overrun checker.

a.c:4: error: Buffer Overrun L4
  Offset: [0, +oo] Size: 2.
  2. void foo() {
  3. int a[2];
  4. for(int i=0; a[i]; i++) {}
                  ^
  5. }

For the example case, it reports L4 issue as above. The reason you did not see the issue is that it suppresses the issue types that are likely to be false positive, e.g. offset or size interval includes an infinity bound like above.

infer/infer/src/base/IssueType.ml

Lines 380 to 382 in 5aeb169

let buffer_overrun_l4 =
register ~enabled:false ~id:"BUFFER_OVERRUN_L4" Error BufferOverrunChecker
~user_documentation:"See [BUFFER_OVERRUN_L1](#buffer_overrun_l1)"

Note that ~enabled:false is given when defining the L4 issue type.

To enable all issue types, you can pass --no-filtering option, or --enable-issue-type to enable each of them.

else if
Bound.is_symbolic (ItvPure.lb real_idx) && Bound.le (ItvPure.lb size) (ItvPure.lb real_idx)
then {report_issue_type= Issue IssueType.buffer_overrun_s2; propagate= true}
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