[PATCH 04/27] Restrict /dev/mem and /dev/kmem when the kernel is locked down
From: jlee@suse.com (joeyli)
Date: 2017-10-20 06:37:45
Also in:
linux-efi, lkml
Hi David, Thanks for you send out this series. On Thu, Oct 19, 2017 at 03:51:02PM +0100, David Howells wrote:
From: Matthew Garrett <redacted> Allowing users to write to address space makes it possible for the kernel to be subverted, avoiding module loading restrictions. Prevent this when the kernel has been locked down. Signed-off-by: Matthew Garrett <redacted> Signed-off-by: David Howells <dhowells@redhat.com>
I have reviewed and tested this patch. Please feel free to add: Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com> Thanks a lot! Joey Lee
quoted hunk ↗ jump to hunk
--- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+)diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 593a8818aca9..b7c36898b689 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c@@ -179,6 +179,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, if (p != *ppos) return -EFBIG; + if (kernel_is_locked_down("/dev/mem")) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT;@@ -540,6 +543,9 @@ 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 (kernel_is_locked_down("/dev/kmem")) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); --To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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