From f60c8fdc9fc718aa799bbdcc4e860e6c18f4ab7b 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 [bwh: Forward-ported to 4.9: adjust context] 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 425a0c1edc09..57746aa00562 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; @@ -514,6 +517,9 @@ 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