From: David Gibson <david@gibson.dropbear.id.au> To: Greg Kurz <groug@kaod.org> Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, Paul Mackerras <paulus@samba.org>, Sam Bobroff <sam.bobroff@au1.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, linuxppc-dev@lists.ozlabs.org, stable@vger.kernel.org Subject: Re: [PATCH] KVM: PPC: fix oops when checking KVM_CAP_PPC_HTM Date: Fri, 15 Sep 2017 10:48:39 +1000 [thread overview] Message-ID: <20170915004839.GA5250@umbus.fritz.box> (raw) In-Reply-To: <150542618501.6859.11512107352972110416.stgit@bahia.lan> [-- Attachment #1: Type: text/plain, Size: 1893 bytes --] On Thu, Sep 14, 2017 at 11:56:25PM +0200, Greg Kurz wrote: > The following program causes a kernel oops: > > #include <sys/types.h> > #include <sys/stat.h> > #include <fcntl.h> > #include <sys/ioctl.h> > #include <linux/kvm.h> > > main() > { > int fd = open("/dev/kvm", O_RDWR); > ioctl(fd, KVM_CHECK_EXTENSION, KVM_CAP_PPC_HTM); > } > > This happens because when using the global KVM fd with > KVM_CHECK_EXTENSION, kvm_vm_ioctl_check_extension() gets > called with a NULL kvm argument, which gets dereferenced > in is_kvmppc_hv_enabled(). Spotted while reading the code. > > Let's use the hv_enabled fallback variable, like everywhere > else in this function. > > Fixes: 23528bb21ee2 ("KVM: PPC: Introduce KVM_CAP_PPC_HTM") > Cc: stable@vger.kernel.org # v4.7+ > Signed-off-by: Greg Kurz <groug@kaod.org> I don't think this is right. I'm pretty sure you want to fall back to hv_enabled *only when* kvm is NULL. Otherwise if you have a PR guest on an HV capable machine, this will give the wrong answer, when called for that specific VM. > --- > arch/powerpc/kvm/powerpc.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c > index 3480faaf1ef8..ee279c7f4802 100644 > --- a/arch/powerpc/kvm/powerpc.c > +++ b/arch/powerpc/kvm/powerpc.c > @@ -644,8 +644,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > break; > #endif > case KVM_CAP_PPC_HTM: > - r = cpu_has_feature(CPU_FTR_TM_COMP) && > - is_kvmppc_hv_enabled(kvm); > + r = cpu_has_feature(CPU_FTR_TM_COMP) && hv_enabled; > break; > default: > r = 0; > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 833 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: David Gibson <david@gibson.dropbear.id.au> To: Greg Kurz <groug@kaod.org> Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, Paul Mackerras <paulus@samba.org>, Sam Bobroff <sam.bobroff@au1.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, linuxppc-dev@lists.ozlabs.org, stable@vger.kernel.org Subject: Re: [PATCH] KVM: PPC: fix oops when checking KVM_CAP_PPC_HTM Date: Fri, 15 Sep 2017 00:48:39 +0000 [thread overview] Message-ID: <20170915004839.GA5250@umbus.fritz.box> (raw) In-Reply-To: <150542618501.6859.11512107352972110416.stgit@bahia.lan> [-- Attachment #1: Type: text/plain, Size: 1893 bytes --] On Thu, Sep 14, 2017 at 11:56:25PM +0200, Greg Kurz wrote: > The following program causes a kernel oops: > > #include <sys/types.h> > #include <sys/stat.h> > #include <fcntl.h> > #include <sys/ioctl.h> > #include <linux/kvm.h> > > main() > { > int fd = open("/dev/kvm", O_RDWR); > ioctl(fd, KVM_CHECK_EXTENSION, KVM_CAP_PPC_HTM); > } > > This happens because when using the global KVM fd with > KVM_CHECK_EXTENSION, kvm_vm_ioctl_check_extension() gets > called with a NULL kvm argument, which gets dereferenced > in is_kvmppc_hv_enabled(). Spotted while reading the code. > > Let's use the hv_enabled fallback variable, like everywhere > else in this function. > > Fixes: 23528bb21ee2 ("KVM: PPC: Introduce KVM_CAP_PPC_HTM") > Cc: stable@vger.kernel.org # v4.7+ > Signed-off-by: Greg Kurz <groug@kaod.org> I don't think this is right. I'm pretty sure you want to fall back to hv_enabled *only when* kvm is NULL. Otherwise if you have a PR guest on an HV capable machine, this will give the wrong answer, when called for that specific VM. > --- > arch/powerpc/kvm/powerpc.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c > index 3480faaf1ef8..ee279c7f4802 100644 > --- a/arch/powerpc/kvm/powerpc.c > +++ b/arch/powerpc/kvm/powerpc.c > @@ -644,8 +644,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > break; > #endif > case KVM_CAP_PPC_HTM: > - r = cpu_has_feature(CPU_FTR_TM_COMP) && > - is_kvmppc_hv_enabled(kvm); > + r = cpu_has_feature(CPU_FTR_TM_COMP) && hv_enabled; > break; > default: > r = 0; > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 833 bytes --]
next prev parent reply other threads:[~2017-09-15 0:48 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-09-14 21:56 [PATCH] KVM: PPC: fix oops when checking KVM_CAP_PPC_HTM Greg Kurz 2017-09-14 21:56 ` Greg Kurz 2017-09-15 0:48 ` David Gibson [this message] 2017-09-15 0:48 ` David Gibson 2017-09-15 5:52 ` Greg Kurz 2017-09-15 5:52 ` Greg Kurz 2017-09-15 5:52 ` Greg Kurz 2017-09-15 6:54 ` Greg Kurz 2017-09-15 6:54 ` Greg Kurz 2017-09-15 8:59 ` David Gibson 2017-09-15 8:59 ` David Gibson 2017-09-18 6:16 ` Thomas Huth 2017-09-18 6:16 ` Thomas Huth 2017-10-12 11:27 ` Michael Ellerman 2017-10-12 11:27 ` Michael Ellerman 2017-10-12 12:51 ` Greg Kurz 2017-10-12 12:51 ` Greg Kurz 2017-10-12 22:20 ` David Gibson 2017-10-12 22:20 ` David Gibson 2017-10-12 23:16 ` Greg Kurz 2017-10-12 23:16 ` Greg Kurz 2017-10-13 16:14 ` Paolo Bonzini 2017-10-13 16:14 ` Paolo Bonzini 2017-10-14 1:23 ` Paul Mackerras 2017-10-14 1:23 ` Paul Mackerras 2017-10-14 1:23 ` Paul Mackerras 2017-10-14 1:23 ` Paul Mackerras
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20170915004839.GA5250@umbus.fritz.box \ --to=david@gibson.dropbear.id.au \ --cc=groug@kaod.org \ --cc=kvm-ppc@vger.kernel.org \ --cc=kvm@vger.kernel.org \ --cc=linuxppc-dev@lists.ozlabs.org \ --cc=paulus@samba.org \ --cc=pbonzini@redhat.com \ --cc=sam.bobroff@au1.ibm.com \ --cc=stable@vger.kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.