From de85ec8b07f82c8c84de7687f769e74bf4c26a1e Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 23 Mar 2017 13:07:16 +0800 Subject: [PATCH 1/4] virtio_pci: fix out of bound access for msix_names Fedora has received multiple reports of crashes when running 4.11 as a guest https://bugzilla.redhat.com/show_bug.cgi?id=1430297 https://bugzilla.redhat.com/show_bug.cgi?id=1434462 https://bugzilla.kernel.org/show_bug.cgi?id=194911 https://bugzilla.redhat.com/show_bug.cgi?id=1433899 The crashes are not always consistent but they are generally some flavor of oops or GPF in virtio related code. Multiple people have done bisections (Thank you Thorsten Leemhuis and Richard W.M. Jones) and found this commit to be at fault 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507 is the first bad commit commit 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507 Author: Christoph Hellwig Date: Sun Feb 5 18:15:19 2017 +0100 virtio_pci: use shared interrupts for virtqueues The issue seems to be an out of bounds access to the msix_names array corrupting kernel memory. Fixes: 07ec51480b5e ("virtio_pci: use shared interrupts for virtqueues") Reported-by: Laura Abbott Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin Reviewed-by: Christoph Hellwig Tested-by: Richard W.M. Jones Tested-by: Thorsten Leemhuis --- drivers/virtio/virtio_pci_common.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c index df548a6fb844f..590534910dc61 100644 --- a/drivers/virtio/virtio_pci_common.c +++ b/drivers/virtio/virtio_pci_common.c @@ -147,7 +147,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs, { struct virtio_pci_device *vp_dev = to_vp_device(vdev); const char *name = dev_name(&vp_dev->vdev.dev); - int i, err = -ENOMEM, allocated_vectors, nvectors; + int i, j, err = -ENOMEM, allocated_vectors, nvectors; unsigned flags = PCI_IRQ_MSIX; bool shared = false; u16 msix_vec; @@ -212,7 +212,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs, if (!vp_dev->msix_vector_map) goto out_disable_config_irq; - allocated_vectors = 1; /* vector 0 is the config interrupt */ + allocated_vectors = j = 1; /* vector 0 is the config interrupt */ for (i = 0; i < nvqs; ++i) { if (!names[i]) { vqs[i] = NULL; @@ -236,18 +236,19 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs, continue; } - snprintf(vp_dev->msix_names[i + 1], + snprintf(vp_dev->msix_names[j], sizeof(*vp_dev->msix_names), "%s-%s", dev_name(&vp_dev->vdev.dev), names[i]); err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec), vring_interrupt, IRQF_SHARED, - vp_dev->msix_names[i + 1], vqs[i]); + vp_dev->msix_names[j], vqs[i]); if (err) { /* don't free this irq on error */ vp_dev->msix_vector_map[i] = VIRTIO_MSI_NO_VECTOR; goto out_remove_vqs; } vp_dev->msix_vector_map[i] = msix_vec; + j++; /* * Use a different vector for each queue if they are available, From fc8653228c8588a120f6b5dad6983b7b61ff669e Mon Sep 17 00:00:00 2001 From: Ladi Prosek Date: Thu, 23 Mar 2017 08:04:18 +0100 Subject: [PATCH 2/4] virtio_balloon: init 1st buffer in stats vq When init_vqs runs, virtio_balloon.stats is either uninitialized or contains stale values. The host updates its state with garbage data because it has no way of knowing that this is just a marker buffer used for signaling. This patch updates the stats before pushing the initial buffer. Alternative fixes: * Push an empty buffer in init_vqs. Not easily done with the current virtio implementation and violates the spec "Driver MUST supply the same subset of statistics in all buffers submitted to the statsq". * Push a buffer with invalid tags in init_vqs. Violates the same spec clause, plus "invalid tag" is not really defined. Note: the spec says: When using the legacy interface, the device SHOULD ignore all values in the first buffer in the statsq supplied by the driver after device initialization. Note: Historically, drivers supplied an uninitialized buffer in the first buffer. Unfortunately QEMU does not seem to implement the recommendation even for the legacy interface. Cc: stable@vger.kernel.org Signed-off-by: Ladi Prosek Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_balloon.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 4e1191508228c..fcd06e16a1a2a 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -429,6 +429,8 @@ static int init_vqs(struct virtio_balloon *vb) * Prime this virtqueue with one buffer so the hypervisor can * use it to signal us later (it can't be broken yet!). */ + update_balloon_stats(vb); + sg_init_one(&sg, vb->stats, sizeof vb->stats); if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) < 0) From 9646b26e85896ef0256e66649f7937f774dc18a6 Mon Sep 17 00:00:00 2001 From: Ladi Prosek Date: Tue, 28 Mar 2017 18:46:58 +0200 Subject: [PATCH 3/4] virtio-balloon: use actual number of stats for stats queue buffers The virtio balloon driver contained a not-so-obvious invariant that update_balloon_stats has to update exactly VIRTIO_BALLOON_S_NR counters in order to send valid stats to the host. This commit fixes it by having update_balloon_stats return the actual number of counters, and its callers use it when pushing buffers to the stats virtqueue. Note that it is still out of spec to change the number of counters at run-time. "Driver MUST supply the same subset of statistics in all buffers submitted to the statsq." Suggested-by: Arnd Bergmann Signed-off-by: Ladi Prosek Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_balloon.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index fcd06e16a1a2a..d9544db231ef3 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -242,11 +242,11 @@ static inline void update_stat(struct virtio_balloon *vb, int idx, #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) -static void update_balloon_stats(struct virtio_balloon *vb) +static unsigned int update_balloon_stats(struct virtio_balloon *vb) { unsigned long events[NR_VM_EVENT_ITEMS]; struct sysinfo i; - int idx = 0; + unsigned int idx = 0; long available; all_vm_events(events); @@ -266,6 +266,8 @@ static void update_balloon_stats(struct virtio_balloon *vb) pages_to_bytes(i.totalram)); update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, pages_to_bytes(available)); + + return idx; } /* @@ -291,14 +293,14 @@ static void stats_handle_request(struct virtio_balloon *vb) { struct virtqueue *vq; struct scatterlist sg; - unsigned int len; + unsigned int len, num_stats; - update_balloon_stats(vb); + num_stats = update_balloon_stats(vb); vq = vb->stats_vq; if (!virtqueue_get_buf(vq, &len)) return; - sg_init_one(&sg, vb->stats, sizeof(vb->stats)); + sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); virtqueue_kick(vq); } @@ -423,15 +425,16 @@ static int init_vqs(struct virtio_balloon *vb) vb->deflate_vq = vqs[1]; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { struct scatterlist sg; + unsigned int num_stats; vb->stats_vq = vqs[2]; /* * Prime this virtqueue with one buffer so the hypervisor can * use it to signal us later (it can't be broken yet!). */ - update_balloon_stats(vb); + num_stats = update_balloon_stats(vb); - sg_init_one(&sg, vb->stats, sizeof vb->stats); + sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) < 0) BUG(); From f0bb2d50dfcc519f06f901aac88502be6ff1df2c Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 28 Mar 2017 18:46:59 +0200 Subject: [PATCH 4/4] virtio_balloon: prevent uninitialized variable use The latest gcc-7.0.1 snapshot reports a new warning: virtio/virtio_balloon.c: In function 'update_balloon_stats': virtio/virtio_balloon.c:258:26: error: 'events[2]' is used uninitialized in this function [-Werror=uninitialized] virtio/virtio_balloon.c:260:26: error: 'events[3]' is used uninitialized in this function [-Werror=uninitialized] virtio/virtio_balloon.c:261:56: error: 'events[18]' is used uninitialized in this function [-Werror=uninitialized] virtio/virtio_balloon.c:262:56: error: 'events[17]' is used uninitialized in this function [-Werror=uninitialized] This seems absolutely right, so we should add an extra check to prevent copying uninitialized stack data into the statistics. >From all I can tell, this has been broken since the statistics code was originally added in 2.6.34. Fixes: 9564e138b1f6 ("virtio: Add memory statistics reporting to the balloon driver (V4)") Signed-off-by: Arnd Bergmann Signed-off-by: Ladi Prosek Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_balloon.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index d9544db231ef3..34adf9b9c0538 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -254,12 +254,14 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb) available = si_mem_available(); +#ifdef CONFIG_VM_EVENT_COUNTERS update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, pages_to_bytes(events[PSWPIN])); update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, pages_to_bytes(events[PSWPOUT])); update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); +#endif update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, pages_to_bytes(i.freeram)); update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,