+ mm-mremap-replace-can_modify_mm-with-can_modify_vma.patch added to mm-unstable branch

+ mm-mremap-replace-can_modify_mm-with-can_modify_vma.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/mremap: replace can_modify_mm with can_modify_vma
has been added to the -mm mm-unstable branch.  Its filename is
     mm-mremap-replace-can_modify_mm-with-can_modify_vma.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mremap-replace-can_modify_mm-with-can_modify_vma.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Pedro Falcato <pedro.falcato@gmail.com>
Subject: mm/mremap: replace can_modify_mm with can_modify_vma
Date: Sat, 17 Aug 2024 01:18:31 +0100

Delegate all can_modify checks to the proper places.  Unmap checks are
done in do_unmap (et al).  The source VMA check is done purposefully
before unmapping, to keep the original mseal semantics.

Link: https://lkml.kernel.org/r/20240817-mseal-depessimize-v3-4-d8d2e037df30@gmail.com
Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mremap.c |   32 ++++++--------------------------
 1 file changed, 6 insertions(+), 26 deletions(-)

--- a/mm/mremap.c~mm-mremap-replace-can_modify_mm-with-can_modify_vma
+++ a/mm/mremap.c
@@ -902,19 +902,6 @@ static unsigned long mremap_to(unsigned
 	if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
 		return -ENOMEM;
 
-	/*
-	 * In mremap_to().
-	 * Move a VMA to another location, check if src addr is sealed.
-	 *
-	 * Place can_modify_mm here because mremap_to()
-	 * does its own checking for address range, and we only
-	 * check the sealing after passing those checks.
-	 *
-	 * can_modify_mm assumes we have acquired the lock on MM.
-	 */
-	if (unlikely(!can_modify_mm(mm, addr, addr + old_len)))
-		return -EPERM;
-
 	if (flags & MREMAP_FIXED) {
 		/*
 		 * In mremap_to().
@@ -1052,6 +1039,12 @@ SYSCALL_DEFINE5(mremap, unsigned long, a
 		goto out;
 	}
 
+	/* Don't allow remapping vmas when they have already been sealed */
+	if (!can_modify_vma(vma)) {
+		ret = -EPERM;
+		goto out;
+	}
+
 	if (is_vm_hugetlb_page(vma)) {
 		struct hstate *h __maybe_unused = hstate_vma(vma);
 
@@ -1079,19 +1072,6 @@ SYSCALL_DEFINE5(mremap, unsigned long, a
 		goto out;
 	}
 
-	/*
-	 * Below is shrink/expand case (not mremap_to())
-	 * Check if src address is sealed, if so, reject.
-	 * In other words, prevent shrinking or expanding a sealed VMA.
-	 *
-	 * Place can_modify_mm here so we can keep the logic related to
-	 * shrink/expand together.
-	 */
-	if (unlikely(!can_modify_mm(mm, addr, addr + old_len))) {
-		ret = -EPERM;
-		goto out;
-	}
-
 	/*
 	 * Always allow a shrinking remap: that just unmaps
 	 * the unnecessary pages..
_

Patches currently in -mm which might be from pedro.falcato@gmail.com are

selftests-mm-add-mseal-test-for-no-discard-madvise.patch
selftests-mm-add-mseal-test-for-no-discard-madvise-fix.patch
mm-move-can_modify_vma-to-mm-vmah.patch
mm-munmap-replace-can_modify_mm-with-can_modify_vma.patch
mm-mprotect-replace-can_modify_mm-with-can_modify_vma.patch
mm-mremap-replace-can_modify_mm-with-can_modify_vma.patch
mseal-replace-can_modify_mm_madv-with-a-vma-variant.patch
mm-remove-can_modify_mm.patch
selftests-mm-add-more-mseal-traversal-tests.patch