The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x e8061f06185be0a06a73760d6526b8b0feadfe52 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024101823-tractor-twitter-a318@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From e8061f06185be0a06a73760d6526b8b0feadfe52 Mon Sep 17 00:00:00 2001 From: Nico Boehr nrb@linux.ibm.com Date: Tue, 17 Sep 2024 17:18:33 +0200 Subject: [PATCH] KVM: s390: gaccess: Check if guest address is in memslot
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
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index e65f597e3044..a688351f4ab5 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -828,6 +828,8 @@ 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 @@ -985,6 +987,8 @@ 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 b320d12aa049..3fde45a151f2 100644 --- a/arch/s390/kvm/gaccess.h +++ b/arch/s390/kvm/gaccess.h @@ -405,11 +405,12 @@ 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. */ @@ -428,11 +429,12 @@ 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. */