Hi, I believe that there is a data race when write/read accessing the file offset (file->f_pos) in the drivers/char/generic_nvram.c and drivers/char/mbcs during the llseek file operation.

The corresponding llseek functions can be found in lines: 34 for generic_nvram.c and 452 for mbcs.c

I am trying to understand if this is a genuine race, but when reading the documentation regarding locking in file_operations (Documentation/filesystem/Locking), it mentions that if you are implementing your own llseek (as in these 2 drivers) you need to synchronise with a lock.

I checked another module that uses the same API (arch/x86/kernel/cpuid.c), and they are indeed protecting the offset access with a mutex during the llseek file operation.

Any thoughts are appreciated.

Thanks