CVE-2024-42084

In the Linux kernel, the following vulnerability has been resolved:

ftruncate: pass a signed offset

The old ftruncate() syscall, using the 32-bit off_t misses a sign extension when called in compat mode on 64-bit architectures. As a result, passing a negative length accidentally succeeds in truncating to file size between 2GiB and 4GiB.

Changing the type of the compat syscall to the signed compatofft changes the behavior so it instead returns -EINVAL.

The native entry point, the truncate() syscall and the corresponding loff_t based variants are all correct already and do not suffer from this mistake.