38 lines
1.1 KiB
Diff
38 lines
1.1 KiB
Diff
From: Matthew Garrett <mjg59@srcf.ucam.org>
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Date: Fri, 9 Mar 2012 09:28:15 -0500
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Subject: [05/18] Restrict /dev/mem and /dev/kmem when securelevel is set.
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Origin: https://github.com/mjg59/linux/commit/401996625d478c814fe9e736ca9e6c5c5f055f06
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Allowing users to write to address space provides mechanisms that may permit
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modification of the kernel at runtime. Prevent this if securelevel has been
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set.
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Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
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[bwh: Forward-ported to 4.10: adjust context]
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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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--- a/drivers/char/mem.c
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+++ b/drivers/char/mem.c
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@@ -164,6 +164,9 @@ static ssize_t write_mem(struct file *fi
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if (p != *ppos)
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return -EFBIG;
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+ if (get_securelevel() > 0)
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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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@@ -514,6 +517,9 @@ static ssize_t write_kmem(struct file *f
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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 (get_securelevel() > 0)
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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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