linux-kernel - [PATCH v3 3/7] mm/mprotect: Replace can_modify_mm with can_modify

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Message-Id: <20240817-mseal-depessimize-v3-3-d8d2e037df30@gmail.com>
Date: Sat, 17 Aug 2024 01:18:30 +0100
From: Pedro Falcato <pedro.falcato@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Vlastimil Babka <vbabka@...e.cz>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Shuah Khan <shuah@...nel.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, jeffxu@...omium.org, oliver.sang@...el.com, 
 torvalds@...ux-foundation.org, Michael Ellerman <mpe@...erman.id.au>, 
 Kees Cook <kees@...nel.org>, Pedro Falcato <pedro.falcato@...il.com>
Subject: [PATCH v3 3/7] mm/mprotect: Replace can_modify_mm with
 can_modify_vma

Avoid taking an extra trip down the mmap tree by checking the vmas
directly. mprotect (per POSIX) tolerates partial failure.

Signed-off-by: Pedro Falcato <pedro.falcato@...il.com>
---
 mm/mprotect.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 446f8e5f10d9..0c5d6d06107d 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -611,6 +611,9 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
 	unsigned long charged = 0;
 	int error;

+	if (!can_modify_vma(vma))
+		return -EPERM;
+
 	if (newflags == oldflags) {
 		*pprev = vma;
 		return 0;
@@ -769,15 +772,6 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		}
 	}

-	/*
-	 * checking if memory is sealed.
-	 * can_modify_mm assumes we have acquired the lock on MM.
-	 */
-	if (unlikely(!can_modify_mm(current->mm, start, end))) {
-		error = -EPERM;
-		goto out;
-	}
-
 	prev = vma_prev(&vmi);
 	if (start > vma->vm_start)
 		prev = vma;

-- 
2.46.0