[ Upstream commit e8061f06185be0a06a73760d6526b8b0feadfe52 ]
Previously, access_guest_page() did not check whether the given guest
address is inside of a memslot. This is not a problem, since
kvm_write_guest_page/kvm_read_guest_page return -EFAULT in this case.
However, -EFAULT is also returned when copy_to/from_user fails.
When emulating a guest instruction, the address being outside a memslot
usually means that an addressing exception should be injected into the
guest.
Failure in copy_to/from_user however indicates that something is wrong
in userspace and hence should be handled there.
To be able to distinguish these two cases, return PGM_ADDRESSING in
access_guest_page() when the guest address is outside guest memory. In
access_guest_real(), populate vcpu->arch.pgm.code such that
kvm_s390_inject_prog_cond() can be used in the caller for injecting into
the guest (if applicable).
Since this adds a new return value to access_guest_page(), we need to make
sure that other callers are not confused by the new positive return value.
There are the following users of access_guest_page():
- access_guest_with_key() does the checking itself (in
guest_range_to_gpas()), so this case should never happen. Even if, the
handling is set up properly.
- access_guest_real() just passes the return code to its callers, which
are:
- read_guest_real() - see below
- write_guest_real() - see below
There are the following users of read_guest_real():
- ar_translation() in gaccess.c which already returns PGM_*
- setup_apcb10(), setup_apcb00(), setup_apcb11() in vsie.c which always
return -EFAULT on read_guest_read() nonzero return - no change
- shadow_crycb(), handle_stfle() always present this as validity, this
could be handled better but doesn't change current behaviour - no change
There are the following users of write_guest_real():
- kvm_s390_store_status_unloaded() always returns -EFAULT on
write_guest_real() failure.
Fixes: 2293897805c2 ("KVM: s390: add architecture compliant guest access functions")
Cc: stable@vger.kernel.org
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20240917151904.74314-2-nrb@linux.ibm.com
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
