arm64: compat: Work around uninitialized variable warning

arm64: compat: Work around uninitialized variable warning

Dan reports that smatch complains about a potential uninitialized
variable being used in the compat alignment fixup code.

The logic is not wrong per se, but we do end up using an uninitialized
variable if reading the instruction that triggered the alignment fault
from user space faults, even if the fault ensures that the uninitialized
value doesn't propagate any further.

Given that we just give up and return 1 if any fault occurs when reading
the instruction, let's get rid of the 'success handling' pattern that
captures the fault in a variable and aborts later, and instead, just
return 1 immediately if any of the get_user() calls result in an
exception.

Fixes: 3fc24ef32d3b ("arm64: compat: Implement misalignment fixups for multiword loads")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/202304021214.gekJ8yRc-lkp@intel.com/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20230404103625.2386382-1-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>