From: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO register
space. This would potentially permit root to trigger arbitrary DMA, so lock
it down by default.
Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
arch/x86/kernel/ioport.c | 5 +++--
drivers/char/mem.c | 4 ++++
2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 589b3193f102..2ee24e9ff6d8 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -15,6 +15,7 @@
#include <linux/thread_info.h>
#include <linux/syscalls.h>
#include <linux/bitmap.h>
+#include <linux/security.h>
#include <asm/syscalls.h>
/*
@@ -28,7 +29,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
return -EINVAL;
- if (turn_on && !capable(CAP_SYS_RAWIO))
+ if (turn_on && (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down()))
return -EPERM;
/*
@@ -108,7 +109,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
return -EINVAL;
/* Trying to gain more privileges? */
if (level > old) {
- if (!capable(CAP_SYS_RAWIO))
+ if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
return -EPERM;
}
regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 5bb1985ec484..17e22cb2db14 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -28,6 +28,7 @@
#include <linux/export.h>
#include <linux/io.h>
#include <linux/uio.h>
+#include <linux/security.h>
#include <linux/uaccess.h>
@@ -580,6 +581,9 @@ static ssize_t write_port(struct file *file, const char __user *buf,
unsigned long i = *ppos;
const char __user *tmp = buf;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (!access_ok(VERIFY_READ, buf, count))
return -EFAULT;
while (count-- > 0 && i < 65536) {
--
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