linux-hardening - [RFC PATCH v1 6/8] mseal mremap

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Date: Mon, 16 Oct 2023 14:38:25 +0000
From: jeffxu@...omium.org
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Subject: [RFC PATCH v1 6/8] mseal mremap

From: Jeff Xu <jeffxu@...gle.com>

check seal for mremap(2)

Signed-off-by: Jeff Xu <jeffxu@...gle.com>
---
 mm/mremap.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/mm/mremap.c b/mm/mremap.c
index e43f9ceaa29d..2288f9d0b126 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -836,7 +836,15 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 	if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
 		return -ENOMEM;
 
+	if (!can_modify_mm(mm, addr, addr + old_len, MM_ACTION_MREMAP,
+			   ON_BEHALF_OF_USERSPACE))
+		return -EACCES;
+
 	if (flags & MREMAP_FIXED) {
+		if (!can_modify_mm(mm, new_addr, new_addr + new_len,
+				   MM_ACTION_MREMAP, ON_BEHALF_OF_USERSPACE))
+			return -EACCES;
+
 		ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
 		if (ret)
 			goto out;
@@ -995,6 +1003,12 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 		goto out;
 	}
 
+	if (!can_modify_mm(mm, addr, addr + old_len, MM_ACTION_MREMAP,
+			   ON_BEHALF_OF_USERSPACE)) {
+		ret = -EACCES;
+		goto out;
+	}
+
 	/*
 	 * Always allow a shrinking remap: that just unmaps
 	 * the unnecessary pages..
-- 
2.42.0.609.gbb76f46606-goog