Messages in this thread Patch in this message | | | Date | Wed, 6 Mar 2019 15:58:50 -0800 | Subject | [PATCH 04/27] Restrict /dev/{mem,kmem,port} when the kernel is locked down | From | Matthew Garrett <> |
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From: Matthew Garrett <mjg59@srcf.ucam.org>
Allowing users to read and write to core kernel memory makes it possible for the kernel to be subverted, avoiding module loading restrictions, and also to steal cryptographic information.
Disallow /dev/mem and /dev/kmem from being opened this when the kernel has been locked down to prevent this.
Also disallow /dev/port from being opened to prevent raw ioport access and thus DMA from being used to accomplish the same thing.
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com> Signed-off-by: Matthew Garrett <matthewgarrett@google.com> --- drivers/char/mem.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index b08dc50f9f26..0a2f2e75d5f4 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -786,6 +786,8 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig) static int open_port(struct inode *inode, struct file *filp) { + if (kernel_is_locked_down("/dev/mem,kmem,port")) + return -EPERM; return capable(CAP_SYS_RAWIO) ? 0 : -EPERM; } -- 2.21.0.352.gf09ad66450-goog
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