From 0b2778d5e59192331351e082a354843b0e9c1235 Mon Sep 17 00:00:00 2001 From: DonatNagyE Date: Thu, 14 Sep 2023 11:51:46 +0200 Subject: [PATCH] [analyzer] Fix StdLibraryFunctionsChecker crash on surprising sink node (#66109) Recent changes in StdLibraryFunctionsChecker introduced a situation where the checker sequentially performed two state transitions to add two separate note tags. In the unlikely case when the updated state (the variable `NewState`) was posteriorly overconstrained, the engine marked the node after the first state transition as a sink to stop the "natural" graph exploration after that point. However, in this particular case the checker tried to directly add a second node, and this triggered an assertion in the `addPredecessor()` method of `ExplodedNode`. This commit introduces an explicit `isSink()` check to avoid this crash. To avoid similar bugs in the future, perhaps it would be possible to tweak `addTransition()` and ensure that it returns `nullptr` when it would return a sink node (to unify the two possible error conditions). This crash was observed in an analysis of the curl project (in a very long and complex function), and there I validated that this is the root cause, but I don't have a self-contained testcase that can trigger the creation of a PosteriorlyOverconstrained node in this situation. --- .../Checkers/StdLibraryFunctionsChecker.cpp | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp index f5f6e3a912376..13bb9cef5e490 100644 --- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp +++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp @@ -1387,8 +1387,8 @@ void StdLibraryFunctionsChecker::checkPostCall(const CallEvent &Call, if (!NewState) continue; - // It is possible that NewState == State is true. - // It can occur if another checker has applied the state before us. + // Here it's possible that NewState == State, e.g. when other checkers + // already applied the same constraints (or stricter ones). // Still add these note tags, the other checker should add only its // specialized note tags. These general note tags are handled always by // StdLibraryFunctionsChecker. @@ -1427,7 +1427,12 @@ void StdLibraryFunctionsChecker::checkPostCall(const CallEvent &Call, }); Pred = C.addTransition(NewState, Pred, Tag); } - if (!Pred) + + // Pred may be: + // - a nullpointer, if we reach an already existing node (theoretically); + // - a sink, when NewState is posteriorly overconstrained. + // In these situations we cannot add the errno note tag. + if (!Pred || Pred->isSink()) continue; }