| Message ID | 1511973506-65683-1-git-send-email-spopovyc@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Fix use after free in HPT resizing code and related minor improvements | expand |
On Wed, Nov 29, 2017 at 11:38:22AM -0500, Serhii Popovych wrote: > It is possible to trigger use after free during HPT resize > causing host kernel to crash. More details and analysis of > the problem can be found in change with corresponding subject > (KVM: PPC: Book3S HV: Fix use after free in case of multiple > resize requests). > > We need some changes to prepare for the fix, especially > make ->error in HPT resize instance single point for > tracking allocation state, improve kvmppc_allocate_hpt() > and kvmppc_free_hpt() so they can be used more safely. > > See individual commit description message to get more > information on changes presented. > > Serhii Popovych (4): > KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt and > cleanups > KVM: PPC: Book3S HV: Improve kvmppc_allocate_hpt()/kvmppc_free_hpt() > KVM: PPC: Book3S HV: Fix use after free in case of multiple resize > requests > KVM: PPC: Book3S HV: Remove redundant parameter from > resize_hpt_release() > > arch/powerpc/kvm/book3s_64_mmu_hv.c | 139 +++++++++++++++++++++--------------- > 1 file changed, 82 insertions(+), 57 deletions(-) Paul, these (at least 1-3) fix (another :() host crash bug which can be triggered by guest and/or userspace actions. Please merge ASAP.
On Wed, Nov 29, 2017 at 11:38:22AM -0500, Serhii Popovych wrote: > It is possible to trigger use after free during HPT resize > causing host kernel to crash. More details and analysis of > the problem can be found in change with corresponding subject > (KVM: PPC: Book3S HV: Fix use after free in case of multiple > resize requests). > > We need some changes to prepare for the fix, especially > make ->error in HPT resize instance single point for > tracking allocation state, improve kvmppc_allocate_hpt() > and kvmppc_free_hpt() so they can be used more safely. > > See individual commit description message to get more > information on changes presented. I spoke with Paul Mackerras about these patches on IRC today. We want this as a fix, ASAP, in 4.15. However, he's uncomfortable with pushing some of extra cleanups which aren't necessary for the bug fix this late for 4.15, and was having trouble following what was the core of the fix. He was also nervous about the addition of more BUG_ON()s. To avoid the round trip to Ukraine time and back, I've made revised versions of patches 1 & 3 which should apply standalone, replaced the BUG_ON()s with WARN_ON()s and revised the commit messages to better explain the crucial part of the fix. However, I've run out of time to test them. Serhii, I'll send you my revised patches shortly. Can you please test them and repost. Then you can rebase patches 2 & 4 from this series on top of the revised patches and post those separately (as a cleanup with less urgency than the actual fix). A couple of people have also suggested CCing kvm@vger.kernel.org on the next round in addition to the lists already included.
David Gibson <david@gibson.dropbear.id.au> writes: > On Wed, Nov 29, 2017 at 11:38:22AM -0500, Serhii Popovych wrote: >> It is possible to trigger use after free during HPT resize >> causing host kernel to crash. More details and analysis of >> the problem can be found in change with corresponding subject >> (KVM: PPC: Book3S HV: Fix use after free in case of multiple >> resize requests). >> >> We need some changes to prepare for the fix, especially >> make ->error in HPT resize instance single point for >> tracking allocation state, improve kvmppc_allocate_hpt() >> and kvmppc_free_hpt() so they can be used more safely. >> >> See individual commit description message to get more >> information on changes presented. > > I spoke with Paul Mackerras about these patches on IRC today. We want > this as a fix, ASAP, in 4.15. However, he's uncomfortable with > pushing some of extra cleanups which aren't necessary for the bug fix > this late for 4.15, and was having trouble following what was the core > of the fix. He was also nervous about the addition of more BUG_ON()s. As was I. > To avoid the round trip to Ukraine time and back, I've made revised > versions of patches 1 & 3 which should apply standalone, replaced the > BUG_ON()s with WARN_ON()s Thanks. cheers
David Gibson wrote: > On Wed, Nov 29, 2017 at 11:38:22AM -0500, Serhii Popovych wrote: >> It is possible to trigger use after free during HPT resize >> causing host kernel to crash. More details and analysis of >> the problem can be found in change with corresponding subject >> (KVM: PPC: Book3S HV: Fix use after free in case of multiple >> resize requests). >> >> We need some changes to prepare for the fix, especially >> make ->error in HPT resize instance single point for >> tracking allocation state, improve kvmppc_allocate_hpt() >> and kvmppc_free_hpt() so they can be used more safely. >> >> See individual commit description message to get more >> information on changes presented. > > I spoke with Paul Mackerras about these patches on IRC today. We want > this as a fix, ASAP, in 4.15. However, he's uncomfortable with > pushing some of extra cleanups which aren't necessary for the bug fix > this late for 4.15, and was having trouble following what was the core > of the fix. He was also nervous about the addition of more BUG_ON()s. Good, no problem, cleanups will be pushed additionally. > > To avoid the round trip to Ukraine time and back, I've made revised > versions of patches 1 & 3 which should apply standalone, replaced the > BUG_ON()s with WARN_ON()s and revised the commit messages to better > explain the crucial part of the fix. > > However, I've run out of time to test them. I did the same test as for this v1 series and found no problem with v2 you sent to me: it seems patch improving kvmppc_allocate_hpt() and kvmppc_free_hpt() isn't actually necessary as I was thinking when submitting v1. > > Serhii, I'll send you my revised patches shortly. Can you please > test them and repost. Then you can rebase patches 2 & 4 from this > series on top of the revised patches and post those separately (as a > cleanup with less urgency than the actual fix). Tested with same test case as with v1: no problem so far. > > A couple of people have also suggested CCing kvm@vger.kernel.org on > the next round in addition to the lists already included. > Done.
It is possible to trigger use after free during HPT resize causing host kernel to crash. More details and analysis of the problem can be found in change with corresponding subject (KVM: PPC: Book3S HV: Fix use after free in case of multiple resize requests). We need some changes to prepare for the fix, especially make ->error in HPT resize instance single point for tracking allocation state, improve kvmppc_allocate_hpt() and kvmppc_free_hpt() so they can be used more safely. See individual commit description message to get more information on changes presented. Serhii Popovych (4): KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt and cleanups KVM: PPC: Book3S HV: Improve kvmppc_allocate_hpt()/kvmppc_free_hpt() KVM: PPC: Book3S HV: Fix use after free in case of multiple resize requests KVM: PPC: Book3S HV: Remove redundant parameter from resize_hpt_release() arch/powerpc/kvm/book3s_64_mmu_hv.c | 139 +++++++++++++++++++++--------------- 1 file changed, 82 insertions(+), 57 deletions(-)