fs: allow positional I/O on files with unsigned offsets

pread64(), pwrite64(), preadv() and pwritev() reject a negative position
with -EINVAL before looking up the file, so FOP_UNSIGNED_OFFSET is never
consulted.  lseek() followed by read() on the same descriptor accepts
the position, and rw_verify_area() already handles it, overflow check
included.  Only the positional syscall wrappers reject it up front.

Check the position after the file lookup and let a negative value
through for files with unsigned offsets, as vfs_setpos_cookie() and
rw_verify_area() do.  Behavior for every other file is unchanged.

On sparc64 userspace is mapped above 2^63, so pread() on /proc/PID/mem
always failed with EINVAL.  pldd(1) could not read a target's memory
because of this, and gdb carries a userspace workaround for the same
thing (PR gdb/30525).

Signed-off-by: Stian Halseth <stian@itx.no>
Link: https://patch.msgid.link/20260917151614.376867-3-stian@itx.no
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions