From 3dfb34906e9e57e70bd497ee21e8d59325c841d2 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 module loading is restricted Allowing users to write to address space makes it possible for the kernel to be subverted, avoiding module loading restrictions. Prevent this when any restrictions have been imposed on loading modules. Signed-off-by: Matthew Garrett --- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 5bb1985..74ee6a4 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -163,6 +163,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, if (p != *ppos) return -EFBIG; + if (secure_modules()) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -515,6 +518,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, if (!pfn_valid(PFN_DOWN(p))) return -EIO; + if (secure_modules()) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 2.7.4