PCI: Lock down BAR access when securelevel is enabled

Any hardware that can potentially generate DMA has to be locked down from
userspace in order to avoid it being possible for an attacker to modify
kernel code. This should be prevented if securelevel has been set. Default
to paranoid - in future we can potentially relax this for sufficiently
IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Gbp-Pq: Topic features/all/securelevel
Gbp-Pq: Name pci-lock-down-bar-access-when-securelevel-is-enabled.patch

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index bcd10c795284cff70a58e73aac8ce2810da6831e..0183f9b3583d38343f4c867ecd9698fe79489cb7 100644 (file)
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -716,6 +716,9 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
        loff_t init_off = off;
        u8 *data = (u8 *) buf;
 
+       if (get_securelevel() > 0)
+               return -EPERM;
+
        if (off > dev->cfg_size)
                return 0;
        if (off + count > dev->cfg_size) {
@@ -1007,6 +1010,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
        resource_size_t start, end;
        int i;
 
+       if (get_securelevel() > 0)
+               return -EPERM;
+
        for (i = 0; i < PCI_ROM_RESOURCE; i++)
                if (res == &pdev->resource[i])
                        break;
@@ -1106,6 +1112,9 @@ 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 (get_securelevel() > 0)
+               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 2408abe4ee8c68919d8a79465e62ab16f3c8660e..27d466a85e5c08afd72d2e032e4e4f2729d2e634 100644 (file)
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -11,6 +11,7 @@
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/capability.h>
+#include <linux/security.h>
 #include <asm/uaccess.h>
 #include <asm/byteorder.h>
 #include "pci.h"
@@ -116,6 +117,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
        int size = dev->cfg_size;
        int cnt;
 
+       if (get_securelevel() > 0)
+               return -EPERM;
+
        if (pos >= size)
                return 0;
        if (nbytes >= size)
@@ -195,6 +199,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
        int ret = 0;
 
+       if (get_securelevel() > 0)
+               return -EPERM;
+
        switch (cmd) {
        case PCIIOC_CONTROLLER:
                ret = pci_domain_nr(dev->bus);
@@ -233,7 +240,7 @@ 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;
 
-       if (!capable(CAP_SYS_RAWIO))
+       if (!capable(CAP_SYS_RAWIO) || (get_securelevel() > 0))
                return -EPERM;
 
        /* Make sure the caller is mapping a real resource for this device */

diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index b91c4da6836574f78df3785ae9ef419b80e069be..9449bdef323ac61aaf5a092d467786a470af1dc2 100644 (file)
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -10,6 +10,7 @@
 #include <linux/errno.h>
 #include <linux/pci.h>
 #include <linux/syscalls.h>
+#include <linux/security.h>
 #include <asm/uaccess.h>
 #include "pci.h"
 
@@ -92,7 +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) || (get_securelevel() > 0))
                return -EPERM;
 
        dev = pci_get_bus_and_slot(bus, dfn);