41 lines
1.4 KiB
Diff
41 lines
1.4 KiB
Diff
From: Matthew Garrett <matthew.garrett@nebula.com>
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Date: Wed, 5 Apr 2017 17:40:30 +0100
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Subject: [43/62] Restrict /dev/mem and /dev/kmem when the kernel is locked
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down
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=104cff827b18e35874153bd8df14eba59e5b411a
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Allowing users to write to address space makes it possible for the kernel to
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be subverted, avoiding module loading restrictions. Prevent this when the
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kernel has been locked down.
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Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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drivers/char/mem.c | 6 ++++++
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1 file changed, 6 insertions(+)
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diff --git a/drivers/char/mem.c b/drivers/char/mem.c
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index 6d9cc2d39d22..f8144049bda3 100644
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--- a/drivers/char/mem.c
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+++ b/drivers/char/mem.c
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@@ -163,6 +163,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
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if (p != *ppos)
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return -EFBIG;
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+ if (kernel_is_locked_down())
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+ return -EPERM;
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+
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if (!valid_phys_addr_range(p, count))
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return -EFAULT;
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@@ -513,6 +516,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
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char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
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int err = 0;
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+ if (kernel_is_locked_down())
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+ return -EPERM;
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+
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if (p < (unsigned long) high_memory) {
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unsigned long to_write = min_t(unsigned long, count,
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(unsigned long)high_memory - p);
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