From 3fab26a9585e895ae41ce6462bc389327f9a0e63 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Mon, 9 Sep 2013 15:49:39 -0700 Subject: [PATCH] Restrict /dev/mem and /dev/kmem when securelevel is set. Orabug: 21539498 Allowing users to write to address space provides mechanisms that may permit modification of the kernel at runtime. Prevent this if securelevel has been set. Signed-off-by: Matthew Garrett Signed-off-by: Santosh Shilimkar --- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 93c08e3e4e33..cca3ab8d89b8 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -167,6 +167,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, if (p != *ppos) return -EFBIG; + if (get_securelevel() > 0) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -513,6 +516,9 @@ 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 (get_securelevel() > 0) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 2.50.1