AIKIDO-2025-10277

TL;DR

The vulnerability lies in the sys_read syscall implementation in the v2 kernel of ZKVM. When handling reads larger than 1024 bytes, the kernel splits the read into smaller chunks. However, it fails to properly update the nwords argument (stored in register a4) during this chunking. As a result, the syscall may read beyond the end of the supplied buffer or not read enough data, leading to undefined or unsafe behavior. The fix ensures that the nwords argument (a4) is correctly updated during large read operations. This prevents incorrect read sizes and avoids reading past buffer boundaries. The patch also enhances test coverage to include reads larger than 1024 bytes, which helps detect this issue during testing.