Fix vms-alpha segfault in image_write_section with fuzzing
This commit fixes a segmentation fault in `image_write_section` for vms-alpha targets within Binutils when encountering malformed object files from fuzzing.
Binutils experienced a segmentation fault in the image_write_section function specifically for vms-alpha targets, triggered by malformed object files created through fuzzing. The root cause was a missing null check for image_section. This commit adds the necessary check, preventing crashes when image_section is null and thus improving the robustness of the vms-alpha object file handling against corrupted inputs.
In Details
The Binutils BFD library (specifically vms-alpha.c) handles object file formats. The image_write_section function is responsible for preparing executable sections for writing. This fix addresses a segfault when PRIV(image_section) (a private data pointer to an asection structure) is NULL, which could occur with fuzzer-generated invalid object files. The added sec == NULL check prevents dereferencing a null pointer, improving the resilience for the vms-alpha target's BFD backend.
For Context
Binutils is a collection of programming tools that helps with tasks like assembling, linking, and analyzing programs. A part of Binutils called BFD is responsible for understanding different object file formats (the compiled code before it becomes a final executable). This commit fixes a crash in Binutils that happened when it tried to process a specific type of corrupted (fuzzed) object file, especially for the older vms-alpha computer architecture. The crash occurred because the software tried to access a piece of data that wasn't there, so the fix adds a check to make sure that data exists before trying to use it, making Binutils more robust when dealing with unusual or damaged input files.