From d7cbb8b1dcc534b8453d7726293a1283434ac17c Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Fri, 9 Mar 2012 09:28:15 -0500 Subject: [PATCH] Restrict /dev/mem and /dev/kmem when securelevel is set. 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 Gbp-Pq: Topic features/all/securelevel Gbp-Pq: Name restrict-dev-mem-and-dev-kmem-when-securelevel-is-se.patch --- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 10f7dbd8a4e2..3803c0dc9f27 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -164,6 +164,9 @@ 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; @@ -510,6 +513,9 @@ 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); -- 2.30.2