Messages in this thread Patch in this message | | | From | Matthew Garrett <> | Subject | [PATCH V2 06/10] Restrict /dev/mem and /dev/kmem in secure boot setups | Date | Thu, 20 Sep 2012 10:41:01 -0400 |
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Allowing users to write to address space makes it possible for the kernel to be subverted. Restrict this when we need to protect the kernel.
Signed-off-by: Matthew Garrett <mjg@redhat.com> --- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1e0a660..33eb947 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -158,6 +158,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, unsigned long copied; void *ptr; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -530,6 +533,9 @@ 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 (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 1.7.11.4
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