Commit 38075679 authored by Pedro Falcato's avatar Pedro Falcato Committed by Andrew Morton
Browse files

mm/mremap: replace can_modify_mm with can_modify_vma 

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: default avatarPedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4a2dd02b

mm/mremap.c

+6 −26
Original line number Diff line number Diff line
@@ -902,19 +902,6 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, 
	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, addr, unsigned long, old_len, 
		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, addr, unsigned long, old_len, 
		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..