From: Suren Baghdasaryan <surenb@google.com>
Date: Wed, 26 Feb 2025 18:55:09 +0000 (-0800)
Subject: userfaultfd: fix PTE unmapping stack-allocated PTE copies
X-Git-Tag: v6.12.20~229
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=99012b24ca232131469de4bb2ec8399315dd56c1;p=thirdparty%2Fkernel%2Fstable.git

userfaultfd: fix PTE unmapping stack-allocated PTE copies

commit 927e926d72d9155fde3264459fe9bfd7b5e40d28 upstream.

Current implementation of move_pages_pte() copies source and destination
PTEs in order to detect concurrent changes to PTEs involved in the move.
However these copies are also used to unmap the PTEs, which will fail if
CONFIG_HIGHPTE is enabled because the copies are allocated on the stack.
Fix this by using the actual PTEs which were kmap()ed.

Link: https://lkml.kernel.org/r/20250226185510.2732648-3-surenb@google.com
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 532f09aacf2b5..080a00d916f6b 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1265,8 +1265,8 @@ retry:
 			spin_unlock(src_ptl);
 
 			if (!locked) {
-				pte_unmap(&orig_src_pte);
-				pte_unmap(&orig_dst_pte);
+				pte_unmap(src_pte);
+				pte_unmap(dst_pte);
 				src_pte = dst_pte = NULL;
 				/* now we can block and wait */
 				folio_lock(src_folio);
@@ -1282,8 +1282,8 @@ retry:
 		/* at this point we have src_folio locked */
 		if (folio_test_large(src_folio)) {
 			/* split_folio() can block */
-			pte_unmap(&orig_src_pte);
-			pte_unmap(&orig_dst_pte);
+			pte_unmap(src_pte);
+			pte_unmap(dst_pte);
 			src_pte = dst_pte = NULL;
 			err = split_folio(src_folio);
 			if (err)
@@ -1308,8 +1308,8 @@ retry:
 				goto out;
 			}
 			if (!anon_vma_trylock_write(src_anon_vma)) {
-				pte_unmap(&orig_src_pte);
-				pte_unmap(&orig_dst_pte);
+				pte_unmap(src_pte);
+				pte_unmap(dst_pte);
 				src_pte = dst_pte = NULL;
 				/* now we can block and wait */
 				anon_vma_lock_write(src_anon_vma);
@@ -1327,8 +1327,8 @@ retry:
 		entry = pte_to_swp_entry(orig_src_pte);
 		if (non_swap_entry(entry)) {
 			if (is_migration_entry(entry)) {
-				pte_unmap(&orig_src_pte);
-				pte_unmap(&orig_dst_pte);
+				pte_unmap(src_pte);
+				pte_unmap(dst_pte);
 				src_pte = dst_pte = NULL;
 				migration_entry_wait(mm, src_pmd, src_addr);
 				err = -EAGAIN;
@@ -1371,8 +1371,8 @@ retry:
 			src_folio = folio;
 			src_folio_pte = orig_src_pte;
 			if (!folio_trylock(src_folio)) {
-				pte_unmap(&orig_src_pte);
-				pte_unmap(&orig_dst_pte);
+				pte_unmap(src_pte);
+				pte_unmap(dst_pte);
 				src_pte = dst_pte = NULL;
 				put_swap_device(si);
 				si = NULL;