Sign extension problem in llseek(2)

In fs/read_write.c:

SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
unsigned long, offset_low, loff_t __user *, result, unsigned int, origin)
...

	offset = vfs_llseek(file, ((loff_t) offset_high << 32) | offset_low,
                        origin);

On a 64-bit system that define CONFIG_HAVE_SYSCALL_WRAPPERS SYSCALL_DEFINEx will truncate long arguments to 32-bit and on some architectures such as MIPS sign-extended to 64-bit again. On such architectures passing a value with bit 31 in offset_low set will result in a huge 64-bit offset being passed to vfs_llseek() and it failiing with EINVAL.

MIPS is affected by this issue. Other 64-bit architectures which also set CONFIG_HAVE_SYSCALL_WRAPPERS and __ARCH_WANT_SYS_LLSEEK are PowerPC, S390 and sparc.

The issue was discovered on Debian's MIPS infrastructure machines running e2fsck:

[...]
This was noticed on one of the Debian
infrastructure machines where, after an upgrade, e2fsck began failing with errors like:

Error reading block 524290 (Invalid argument) while getting next inode from scan. Ignore error<y>?
[...]

Ralf