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: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: linux-pci@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 6d27475e39b2b9ab77f95c7e7b6e3f67d2881991..ec103a7e13fc4020daa08ade916389403a65dd22 100644 (file)
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -903,6 +903,11 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
        unsigned int size = count;
        loff_t init_off = off;
        u8 *data = (u8 *) buf;
+       int ret;
+
+       ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+       if (ret)
+               return ret;
 
        if (off > dev->cfg_size)
                return 0;
@@ -1164,6 +1169,11 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
        int bar = (unsigned long)attr->private;
        enum pci_mmap_state mmap_type;
        struct resource *res = &pdev->resource[bar];
+       int ret;
+
+       ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+       if (ret)
+               return ret;
 
        if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
                return -EINVAL;
@@ -1240,6 +1250,12 @@ 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)
 {
+       int ret;
+
+       ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+       if (ret)
+               return ret;
+
        return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 

diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 445b51db75b0030e287860b6e9363a08a9a85d4e..e29b0d5ced6270294cfa130836125283bb01191a 100644 (file)
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -13,6 +13,7 @@
 #include <linux/seq_file.h>
 #include <linux/capability.h>
 #include <linux/uaccess.h>
+#include <linux/security.h>
 #include <asm/byteorder.h>
 #include "pci.h"
 
@@ -115,7 +116,11 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
        struct pci_dev *dev = PDE_DATA(ino);
        int pos = *ppos;
        int size = dev->cfg_size;
-       int cnt;
+       int cnt, ret;
+
+       ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+       if (ret)
+               return ret;
 
        if (pos >= size)
                return 0;
@@ -196,6 +201,10 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
        int ret = 0;
 
+       ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+       if (ret)
+               return ret;
+
        switch (cmd) {
        case PCIIOC_CONTROLLER:
                ret = pci_domain_nr(dev->bus);
@@ -238,7 +247,8 @@ 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) ||
+           security_locked_down(LOCKDOWN_PCI_ACCESS))
                return -EPERM;
 
        if (fpriv->mmap_state == pci_mmap_io) {

diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index d96626c614f5674b4de24b1c11bcb13a456a6ca5..31e39558d49d81e98b48a62d57f4563e5ae9a213 100644 (file)
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -7,6 +7,7 @@
 
 #include <linux/errno.h>
 #include <linux/pci.h>
+#include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include "pci.h"
@@ -90,7 +91,8 @@ 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) ||
+           security_locked_down(LOCKDOWN_PCI_ACCESS))
                return -EPERM;
 
        dev = pci_get_domain_bus_and_slot(0, bus, dfn);

diff --git a/include/linux/security.h b/include/linux/security.h
index 80ac7fb27aa998b11b70afb6e4f01089d5b914b6..2b763f0ee35272ab53daeb759d4bb684510f243e 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -107,6 +107,7 @@ enum lockdown_reason {
        LOCKDOWN_DEV_MEM,
        LOCKDOWN_KEXEC,
        LOCKDOWN_HIBERNATION,
+       LOCKDOWN_PCI_ACCESS,
        LOCKDOWN_INTEGRITY_MAX,
        LOCKDOWN_CONFIDENTIALITY_MAX,
 };

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 3462f7edcaac1e8424d2d87469aea1385b7476eb..410e90eda848adc76be71b82808bec7a0396294e 100644 (file)
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -22,6 +22,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
        [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
        [LOCKDOWN_KEXEC] = "kexec of unsigned images",
        [LOCKDOWN_HIBERNATION] = "hibernation",
+       [LOCKDOWN_PCI_ACCESS] = "direct PCI access",
        [LOCKDOWN_INTEGRITY_MAX] = "integrity",
        [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };