kubsan4

Usage

Overview

kubsan detects undefined behavior at runtime inside the kernel. Detected undefined behavior is printed to the system console, including the offending line in the source code.

By default, kubsan is not enabled but instead requires the following line to be present in the kernel configuration:

option KUBSAN

The following undefined behavior is detected:

Float cast overflow

The conversion from a floating point to an integer cannot be represented by the destination type.

Integer overflow

The result of an arithmetic computation on two integer operands cannot be represented by the destination type.

Negate overflow

Negation of an integer cannot be represented by the destination type.

Pointer overflow

Pointer arithmetic overflow.

Out of bounds

Array indexing out of bounds, limited to cases where the size of the array can be statically determined.

Shift out of bounds

Undefined logical shift caused by:

• The shift amount being negative.

• The shift operand being negative.

• The shift amount exceeds the number of bits as given by the shift operand type.

• The result of the shift computation cannot be represented by the destination type.

Non-null argument

Passing NULL as the value for a function argument annotated with __nonnull__.

Invalid builtin

Passing zero to a compiler builtin where not allowed.

Invalid load

Loading a value that cannot be represented by the destination type.

Type mismatch

Mismatch between pointer and value type caused by:

• A pointer which does not fulfill the alignment requirements of the value type.

• A pointer to an address which lacks sufficient space to store the value type.

Unreachable

Execution reached passed a function annotated with __dead.

Caveats

The kubsan implementation is limited to architectures using clang(1) as their default compiler.