linux-hardening - [RFC PATCH v3 05/11] mseal: add MM_SEAL_PROT

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Date: Tue, 12 Dec 2023 23:16:59 +0000
From: jeffxu@...omium.org
To: akpm@...ux-foundation.org,
	keescook@...omium.org,
	jannh@...gle.com,
	sroettger@...gle.com,
	willy@...radead.org,
	gregkh@...uxfoundation.org,
	torvalds@...ux-foundation.org
Cc: jeffxu@...gle.com,
	jorgelo@...omium.org,
	groeck@...omium.org,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-mm@...ck.org,
	pedro.falcato@...il.com,
	dave.hansen@...el.com,
	linux-hardening@...r.kernel.org,
	deraadt@...nbsd.org,
	Jeff Xu <jeffxu@...omium.org>
Subject: [RFC PATCH v3 05/11] mseal: add MM_SEAL_PROT_PKEY

From: Jeff Xu <jeffxu@...omium.org>

Seal PROT and PKEY of the address range, in other words, mprotect()
and pkey_mprotect() will be denied if the memory is sealed with
MM_SEAL_PROT_PKEY.

Signed-off-by: Jeff Xu <jeffxu@...omium.org>
---
 mm/mprotect.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index b94fbb45d5c7..1527188b1e92 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -32,6 +32,7 @@
 #include <linux/sched/sysctl.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/memory-tiers.h>
+#include <uapi/linux/mman.h>
 #include <asm/cacheflush.h>
 #include <asm/mmu_context.h>
 #include <asm/tlbflush.h>
@@ -753,6 +754,15 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		}
 	}
 
+	/*
+	 * checking if PROT and PKEY is sealed.
+	 * can_modify_mm assumes we have acquired the lock on MM.
+	 */
+	if (!can_modify_mm(current->mm, start, end, MM_SEAL_PROT_PKEY)) {
+		error = -EACCES;
+		goto out;
+	}
+
 	prev = vma_prev(&vmi);
 	if (start > vma->vm_start)
 		prev = vma;
-- 
2.43.0.472.g3155946c3a-goog