Allowing users to write to address space makes it possible for the kernel
to be subverted. Restrict this when we need to protect the kernel.
Signed-off-by: Matthew Garrett <mjg@xxxxxxxxxx>
---
drivers/char/mem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 8f5f872..c1de8e1 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -158,6 +158,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
unsigned long copied;
void *ptr;
+ if (!capable(CAP_SECURE_FIRMWARE))
+ return -EPERM;
+
if (!valid_phys_addr_range(p, count))
return -EFAULT;
@@ -530,6 +533,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
int err = 0;
+ if (!capable(CAP_SECURE_FIRMWARE))
+ return -EPERM;
+
if (p < (unsigned long) high_memory) {
unsigned long to_write = min_t(unsigned long, count,
(unsigned long)high_memory - p);
--
1.7.11.4
--
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