PCI: Lock down BAR access when the kernel is locked down

Any hardware that can potentially generate DMA has to be locked down in
order to avoid it being possible for an attacker to modify kernel code,
allowing them to circumvent disabled module loading or module signing.
Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
[bwh: For 4.12, adjust context]

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0049-PCI-Lock-down-BAR-access-when-the-kernel-is-locked-d.patch

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 00fa4278c1f49c22d97451759ff0708016523830..055cb4321d4c3909ba4c140f15ef11214f6bab1b 100644 (file)
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -889,6 +889,9 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
        loff_t init_off = off;
        u8 *data = (u8 *) buf;
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        if (off > dev->cfg_size)
                return 0;
        if (off + count > dev->cfg_size) {
@@ -1183,6 +1186,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
        enum pci_mmap_state mmap_type;
        struct resource *res = &pdev->resource[bar];
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
                return -EINVAL;
 
@@ -1263,6 +1269,9 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
                                     struct bin_attribute *attr, char *buf,
                                     loff_t off, size_t count)
 {
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 

diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 58a662e3c4a667ee62fbba934cdc84d0ed72fa84..af56853da13f8cb18ddf6dbea5ede0feee040dbb 100644 (file)
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -117,6 +117,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
        int size = dev->cfg_size;
        int cnt;
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        if (pos >= size)
                return 0;
        if (nbytes >= size)
@@ -196,6 +199,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
        int ret = 0;
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        switch (cmd) {
        case PCIIOC_CONTROLLER:
                ret = pci_domain_nr(dev->bus);
@@ -237,7 +243,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
        struct pci_filp_private *fpriv = file->private_data;
        int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
 
-       if (!capable(CAP_SYS_RAWIO))
+       if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
                return -EPERM;
 
        if (fpriv->mmap_state == pci_mmap_io) {

diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index 83efa001c2e78fd7b8c30855ac5f48273ebcd505..1d9258b9ce9cba7ab339b6d1362bab49665d9907 100644 (file)
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -93,7 +93,7 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
        u32 dword;
        int err = 0;
 
-       if (!capable(CAP_SYS_ADMIN))
+       if (!capable(CAP_SYS_ADMIN) || kernel_is_locked_down())
                return -EPERM;
 
        dev = pci_get_bus_and_slot(bus, dfn);