Comment 3 for bug 1810433

This seems related to commit 58cfa6c2e6eb51b23cc98f8, where this was fixed for the write() syscall. In that commit message the author writes "Q. Do pread64/pwrite64 need to be changed similarly? A. Experiment suggests not: both linux and linux-user yield -1 for NULL 0-length reads/writes." That doesn't match your results, though, and looking at the source both write and pwrite syscalls go through the vfs_write() function, so their behaviour for a NULL/0 buffer should be identical.