[analyzer] Fix crash on using bitcast(<type>, <array>) as array subscript
#101647
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
clang
|
@llvm/pr-subscribers-clang-static-analyzer-1 Author: Pavel Skripkin (pskrgag) ChangesCurrent CSA logic does not expect Catch such cases and return Closes #94496 Full diff: https://github.com/llvm/llvm-project/pull/101647.diff 2 Files Affected:
diff --git a/clang/lib/StaticAnalyzer/Core/Store.cpp b/clang/lib/StaticAnalyzer/Core/Store.cpp
index 67ca61bb56ba2..72587ef31a17c 100644
--- a/clang/lib/StaticAnalyzer/Core/Store.cpp
+++ b/clang/lib/StaticAnalyzer/Core/Store.cpp
@@ -472,7 +472,19 @@ SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset,
const auto *ElemR = dyn_cast<ElementRegion>(BaseRegion);
// Convert the offset to the appropriate size and signedness.
- Offset = svalBuilder.convertToArrayIndex(Offset).castAs<NonLoc>();
+ auto Off = svalBuilder.convertToArrayIndex(Offset).getAs<NonLoc>();
+ if (!Off) {
+ // Handle cases when LazyCompoundVal is used for an array index.
+ // Such case is possible if code does:
+ //
+ // char b[4];
+ // a[__builtin_bitcast(int, b)];
+ //
+ // Return UnknownVal, since we cannot model it.
+ return UnknownVal();
+ }
+
+ Offset = Off.value();
if (!ElemR) {
// If the base region is not an ElementRegion, create one.
diff --git a/clang/test/Analysis/exercise-ps.c b/clang/test/Analysis/exercise-ps.c
index d1e1771afddb5..9bba16c282967 100644
--- a/clang/test/Analysis/exercise-ps.c
+++ b/clang/test/Analysis/exercise-ps.c
@@ -30,3 +30,10 @@ void f3(void *dest) {
void *src = __builtin_alloca(5);
memcpy(dest, src, 1); // expected-warning{{2nd function call argument is a pointer to uninitialized value}}
}
+
+// Reproduce crash from GH#94496. When array is used as subcript to another array, CSA cannot model it
+// and should just assume it's unknown and do not crash.
+void f4(char *array) {
+ char b[4] = {0};
+ array[__builtin_bit_cast(int, b)] = 0x10; // no crash
+}
|
|
@llvm/pr-subscribers-clang Author: Pavel Skripkin (pskrgag) ChangesCurrent CSA logic does not expect Catch such cases and return Closes #94496 Full diff: https://github.com/llvm/llvm-project/pull/101647.diff 2 Files Affected:
diff --git a/clang/lib/StaticAnalyzer/Core/Store.cpp b/clang/lib/StaticAnalyzer/Core/Store.cpp
index 67ca61bb56ba2..72587ef31a17c 100644
--- a/clang/lib/StaticAnalyzer/Core/Store.cpp
+++ b/clang/lib/StaticAnalyzer/Core/Store.cpp
@@ -472,7 +472,19 @@ SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset,
const auto *ElemR = dyn_cast<ElementRegion>(BaseRegion);
// Convert the offset to the appropriate size and signedness.
- Offset = svalBuilder.convertToArrayIndex(Offset).castAs<NonLoc>();
+ auto Off = svalBuilder.convertToArrayIndex(Offset).getAs<NonLoc>();
+ if (!Off) {
+ // Handle cases when LazyCompoundVal is used for an array index.
+ // Such case is possible if code does:
+ //
+ // char b[4];
+ // a[__builtin_bitcast(int, b)];
+ //
+ // Return UnknownVal, since we cannot model it.
+ return UnknownVal();
+ }
+
+ Offset = Off.value();
if (!ElemR) {
// If the base region is not an ElementRegion, create one.
diff --git a/clang/test/Analysis/exercise-ps.c b/clang/test/Analysis/exercise-ps.c
index d1e1771afddb5..9bba16c282967 100644
--- a/clang/test/Analysis/exercise-ps.c
+++ b/clang/test/Analysis/exercise-ps.c
@@ -30,3 +30,10 @@ void f3(void *dest) {
void *src = __builtin_alloca(5);
memcpy(dest, src, 1); // expected-warning{{2nd function call argument is a pointer to uninitialized value}}
}
+
+// Reproduce crash from GH#94496. When array is used as subcript to another array, CSA cannot model it
+// and should just assume it's unknown and do not crash.
+void f4(char *array) {
+ char b[4] = {0};
+ array[__builtin_bit_cast(int, b)] = 0x10; // no crash
+}
|
steakhal
requested changes
Aug 2, 2024
steakhal
approved these changes
Aug 2, 2024
steakhal
changed the title
bitcast(<type>, <array>) as array subscriptbitcast(<type>, <array>) as array subscript
|
Backporting to clang-19 in #101684 |
tru
pushed a commit
to steakhal/llvm-project
that referenced
this pull request
Aug 4, 2024
…script (llvm#101647) Current CSA logic does not expect `LazyCompoundValKind` as array index. This may happen if array is used as subscript to another, in case of bitcast to integer type. Catch such cases and return `UnknownVal`, since CSA cannot model array -> int casts. Closes llvm#94496 (cherry picked from commit d96569e)
|
Thanks! Appreciate the fix. |
banach-space
pushed a commit
to banach-space/llvm-project
that referenced
this pull request
Aug 7, 2024
…script (llvm#101647) Current CSA logic does not expect `LazyCompoundValKind` as array index. This may happen if array is used as subscript to another, in case of bitcast to integer type. Catch such cases and return `UnknownVal`, since CSA cannot model array -> int casts. Closes llvm#94496
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Current CSA logic does not expect
LazyCompoundValKindas array index. This may happen if array is used as subscript to another, in case of bitcast to integer type.Catch such cases and return
UnknownVal, since CSA cannot model array ->int casts.
Closes #94496