From bc93b9ae0151ae5ad5b8504cdc598428ea99570b Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Mon, 17 Aug 2020 11:08:18 -0600 Subject: [PATCH] vfio-pci: Avoid recursive read-lock usage A down_read on memory_lock is held when performing read/write accesses to MMIO BAR space, including across the copy_to/from_user() callouts which may fault. If the user buffer for these copies resides in an mmap of device MMIO space, the mmap fault handler will acquire a recursive read-lock on memory_lock. Avoid this by reducing the lock granularity. Sequential accesses requiring multiple ioread/iowrite cycles are expected to be rare, therefore typical accesses should not see additional overhead. VGA MMIO accesses are expected to be non-fatal regardless of the PCI memory enable bit to allow legacy probing, this behavior remains with a comment added. ioeventfds are now included in memory access testing, with writes dropped while memory space is disabled. Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory") Reported-by: Zhiyi Guo Tested-by: Zhiyi Guo Reviewed-by: Cornelia Huck Signed-off-by: Alex Williamson --- drivers/vfio/pci/vfio_pci_private.h | 2 + drivers/vfio/pci/vfio_pci_rdwr.c | 120 ++++++++++++++++++++++++++++-------- 2 files changed, 98 insertions(+), 24 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h index 86a02af..61ca8ab 100644 --- a/drivers/vfio/pci/vfio_pci_private.h +++ b/drivers/vfio/pci/vfio_pci_private.h @@ -33,12 +33,14 @@ struct vfio_pci_ioeventfd { struct list_head next; + struct vfio_pci_device *vdev; struct virqfd *virqfd; void __iomem *addr; uint64_t data; loff_t pos; int bar; int count; + bool test_mem; }; struct vfio_pci_irq_ctx { diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c index 916b184..9e353c4 100644 --- a/drivers/vfio/pci/vfio_pci_rdwr.c +++ b/drivers/vfio/pci/vfio_pci_rdwr.c @@ -37,17 +37,70 @@ #define vfio_ioread8 ioread8 #define vfio_iowrite8 iowrite8 +#define VFIO_IOWRITE(size) \ +static int vfio_pci_iowrite##size(struct vfio_pci_device *vdev, \ + bool test_mem, u##size val, void __iomem *io) \ +{ \ + if (test_mem) { \ + down_read(&vdev->memory_lock); \ + if (!__vfio_pci_memory_enabled(vdev)) { \ + up_read(&vdev->memory_lock); \ + return -EIO; \ + } \ + } \ + \ + vfio_iowrite##size(val, io); \ + \ + if (test_mem) \ + up_read(&vdev->memory_lock); \ + \ + return 0; \ +} + +VFIO_IOWRITE(8) +VFIO_IOWRITE(16) +VFIO_IOWRITE(32) +#ifdef iowrite64 +VFIO_IOWRITE(64) +#endif + +#define VFIO_IOREAD(size) \ +static int vfio_pci_ioread##size(struct vfio_pci_device *vdev, \ + bool test_mem, u##size *val, void __iomem *io) \ +{ \ + if (test_mem) { \ + down_read(&vdev->memory_lock); \ + if (!__vfio_pci_memory_enabled(vdev)) { \ + up_read(&vdev->memory_lock); \ + return -EIO; \ + } \ + } \ + \ + *val = vfio_ioread##size(io); \ + \ + if (test_mem) \ + up_read(&vdev->memory_lock); \ + \ + return 0; \ +} + +VFIO_IOREAD(8) +VFIO_IOREAD(16) +VFIO_IOREAD(32) + /* * Read or write from an __iomem region (MMIO or I/O port) with an excluded * range which is inaccessible. The excluded range drops writes and fills * reads with -1. This is intended for handling MSI-X vector tables and * leftover space for ROM BARs. */ -static ssize_t do_io_rw(void __iomem *io, char __user *buf, +static ssize_t do_io_rw(struct vfio_pci_device *vdev, bool test_mem, + void __iomem *io, char __user *buf, loff_t off, size_t count, size_t x_start, size_t x_end, bool iswrite) { ssize_t done = 0; + int ret; while (count) { size_t fillable, filled; @@ -66,9 +119,15 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf, if (copy_from_user(&val, buf, 4)) return -EFAULT; - vfio_iowrite32(val, io + off); + ret = vfio_pci_iowrite32(vdev, test_mem, + val, io + off); + if (ret) + return ret; } else { - val = vfio_ioread32(io + off); + ret = vfio_pci_ioread32(vdev, test_mem, + &val, io + off); + if (ret) + return ret; if (copy_to_user(buf, &val, 4)) return -EFAULT; @@ -82,9 +141,15 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf, if (copy_from_user(&val, buf, 2)) return -EFAULT; - vfio_iowrite16(val, io + off); + ret = vfio_pci_iowrite16(vdev, test_mem, + val, io + off); + if (ret) + return ret; } else { - val = vfio_ioread16(io + off); + ret = vfio_pci_ioread16(vdev, test_mem, + &val, io + off); + if (ret) + return ret; if (copy_to_user(buf, &val, 2)) return -EFAULT; @@ -98,9 +163,15 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf, if (copy_from_user(&val, buf, 1)) return -EFAULT; - vfio_iowrite8(val, io + off); + ret = vfio_pci_iowrite8(vdev, test_mem, + val, io + off); + if (ret) + return ret; } else { - val = vfio_ioread8(io + off); + ret = vfio_pci_ioread8(vdev, test_mem, + &val, io + off); + if (ret) + return ret; if (copy_to_user(buf, &val, 1)) return -EFAULT; @@ -178,14 +249,6 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf, count = min(count, (size_t)(end - pos)); - if (res->flags & IORESOURCE_MEM) { - down_read(&vdev->memory_lock); - if (!__vfio_pci_memory_enabled(vdev)) { - up_read(&vdev->memory_lock); - return -EIO; - } - } - if (bar == PCI_ROM_RESOURCE) { /* * The ROM can fill less space than the BAR, so we start the @@ -213,7 +276,8 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf, x_end = vdev->msix_offset + vdev->msix_size; } - done = do_io_rw(io, buf, pos, count, x_start, x_end, iswrite); + done = do_io_rw(vdev, res->flags & IORESOURCE_MEM, io, buf, pos, + count, x_start, x_end, iswrite); if (done >= 0) *ppos += done; @@ -221,9 +285,6 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf, if (bar == PCI_ROM_RESOURCE) pci_unmap_rom(pdev, io); out: - if (res->flags & IORESOURCE_MEM) - up_read(&vdev->memory_lock); - return done; } @@ -278,7 +339,12 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf, return ret; } - done = do_io_rw(iomem, buf, off, count, 0, 0, iswrite); + /* + * VGA MMIO is a legacy, non-BAR resource that hopefully allows + * probing, so we don't currently worry about access in relation + * to the memory enable bit in the command register. + */ + done = do_io_rw(vdev, false, iomem, buf, off, count, 0, 0, iswrite); vga_put(vdev->pdev, rsrc); @@ -296,17 +362,21 @@ static int vfio_pci_ioeventfd_handler(void *opaque, void *unused) switch (ioeventfd->count) { case 1: - vfio_iowrite8(ioeventfd->data, ioeventfd->addr); + vfio_pci_iowrite8(ioeventfd->vdev, ioeventfd->test_mem, + ioeventfd->data, ioeventfd->addr); break; case 2: - vfio_iowrite16(ioeventfd->data, ioeventfd->addr); + vfio_pci_iowrite16(ioeventfd->vdev, ioeventfd->test_mem, + ioeventfd->data, ioeventfd->addr); break; case 4: - vfio_iowrite32(ioeventfd->data, ioeventfd->addr); + vfio_pci_iowrite32(ioeventfd->vdev, ioeventfd->test_mem, + ioeventfd->data, ioeventfd->addr); break; #ifdef iowrite64 case 8: - vfio_iowrite64(ioeventfd->data, ioeventfd->addr); + vfio_pci_iowrite64(ioeventfd->vdev, ioeventfd->test_mem, + ioeventfd->data, ioeventfd->addr); break; #endif } @@ -378,11 +448,13 @@ long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset, goto out_unlock; } + ioeventfd->vdev = vdev; ioeventfd->addr = vdev->barmap[bar] + pos; ioeventfd->data = data; ioeventfd->pos = pos; ioeventfd->bar = bar; ioeventfd->count = count; + ioeventfd->test_mem = vdev->pdev->resource[bar].flags & IORESOURCE_MEM; ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler, NULL, NULL, &ioeventfd->virqfd, fd); -- 2.7.4