This is a note to let you know that I've just added the patch titled
KVM: s390: gaccess: Check if guest address is in memslot
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-s390-gaccess-check-if-guest-address-is-in-memslo.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4ec875243403f7329718f322210b4be8380adb3f
Author: Nico Boehr <nrb@xxxxxxxxxxxxx>
Date: Tue Sep 17 17:18:33 2024 +0200
KVM: s390: gaccess: Check if guest address is in memslot
[ 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@xxxxxxxxxxxxxxx
Signed-off-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
Reviewed-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240917151904.74314-2-nrb@xxxxxxxxxxxxx
Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 6ba82fe0776f8..11ddac5e3e923 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -873,6 +873,8 @@ static int access_guest_page(struct kvm *kvm, enum gacc_mode mode, gpa_t gpa,
const gfn_t gfn = gpa_to_gfn(gpa);
int rc;
+ if (!gfn_to_memslot(kvm, gfn))
+ return PGM_ADDRESSING;
if (mode == GACC_STORE)
rc = kvm_write_guest_page(kvm, gfn, data, offset, len);
else
@@ -936,6 +938,8 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
gra += fragment_len;
data += fragment_len;
}
+ if (rc > 0)
+ vcpu->arch.pgm.code = rc;
return rc;
}
diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
index 4c56de5429608..6c97cde8623a4 100644
--- a/arch/s390/kvm/gaccess.h
+++ b/arch/s390/kvm/gaccess.h
@@ -344,11 +344,12 @@ int read_guest_abs(struct kvm_vcpu *vcpu, unsigned long gpa, void *data,
* @len: number of bytes to copy
*
* Copy @len bytes from @data (kernel space) to @gra (guest real address).
- * It is up to the caller to ensure that the entire guest memory range is
- * valid memory before calling this function.
* Guest low address and key protection are not checked.
*
- * Returns zero on success or -EFAULT on error.
+ * Returns zero on success, -EFAULT when copying from @data failed, or
+ * PGM_ADRESSING in case @gra is outside a memslot. In this case, pgm check info
+ * is also stored to allow injecting into the guest (if applicable) using
+ * kvm_s390_inject_prog_cond().
*
* If an error occurs data may have been copied partially to guest memory.
*/
@@ -367,11 +368,12 @@ int write_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
* @len: number of bytes to copy
*
* Copy @len bytes from @gra (guest real address) to @data (kernel space).
- * It is up to the caller to ensure that the entire guest memory range is
- * valid memory before calling this function.
* Guest key protection is not checked.
*
- * Returns zero on success or -EFAULT on error.
+ * Returns zero on success, -EFAULT when copying to @data failed, or
+ * PGM_ADRESSING in case @gra is outside a memslot. In this case, pgm check info
+ * is also stored to allow injecting into the guest (if applicable) using
+ * kvm_s390_inject_prog_cond().
*
* If an error occurs data may have been copied partially to kernel space.
*/
