+ mm-memremap_pages-convert-to-struct-range-fix.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/hmm/test: use after free in dmirror_allocate_chunk()
has been added to the -mm tree.  Its filename is
     mm-memremap_pages-convert-to-struct-range-fix.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-memremap_pages-convert-to-struct-range-fix.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-memremap_pages-convert-to-struct-range-fix.patch

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------------------------------------------------------
From: Dan Carpenter <dan.carpenter@oracle.com>
Subject: mm/hmm/test: use after free in dmirror_allocate_chunk()

The error handling code does this:

err_free:
	kfree(devmem);
        ^^^^^^^^^^^^^
err_release:
	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
                           ^^^^^^^^
The problem is that when we use "devmem->pagemap.range.start" the
"devmem" pointer is either NULL or freed.

Neither the allocation nor the call to request_free_mem_region() has to
be done under the lock so I moved those to the start of the function.

Link: https://lkml.kernel.org/r/20200926121402.GA7467@kadam
Fixes: 1f9c4bb986d9 ("mm/memremap_pages: convert to 'struct range'")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Cc: Markus Elfring <Markus.Elfring@web.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/test_hmm.c |   42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

--- a/lib/test_hmm.c~mm-memremap_pages-convert-to-struct-range-fix
+++ a/lib/test_hmm.c
@@ -460,6 +460,21 @@ static bool dmirror_allocate_chunk(struc
 	unsigned long pfn_last;
 	void *ptr;
 
+	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
+	if (!devmem)
+		return -ENOMEM;
+
+	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
+				      "hmm_dmirror");
+	if (IS_ERR(res))
+		goto err_devmem;
+
+	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	devmem->pagemap.range.start = res->start;
+	devmem->pagemap.range.end = res->end;
+	devmem->pagemap.ops = &dmirror_devmem_ops;
+	devmem->pagemap.owner = mdevice;
+
 	mutex_lock(&mdevice->devmem_lock);
 
 	if (mdevice->devmem_count == mdevice->devmem_capacity) {
@@ -472,29 +487,14 @@ static bool dmirror_allocate_chunk(struc
 				sizeof(new_chunks[0]) * new_capacity,
 				GFP_KERNEL);
 		if (!new_chunks)
-			goto err;
+			goto err_release;
 		mdevice->devmem_capacity = new_capacity;
 		mdevice->devmem_chunks = new_chunks;
 	}
 
-	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
-					"hmm_dmirror");
-	if (IS_ERR(res))
-		goto err;
-
-	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
-	if (!devmem)
-		goto err_release;
-
-	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
-	devmem->pagemap.range.start = res->start;
-	devmem->pagemap.range.end = res->end;
-	devmem->pagemap.ops = &dmirror_devmem_ops;
-	devmem->pagemap.owner = mdevice;
-
 	ptr = memremap_pages(&devmem->pagemap, numa_node_id());
 	if (IS_ERR(ptr))
-		goto err_free;
+		goto err_release;
 
 	devmem->mdevice = mdevice;
 	pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
@@ -525,12 +525,12 @@ static bool dmirror_allocate_chunk(struc
 
 	return true;
 
-err_free:
-	kfree(devmem);
 err_release:
-	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
-err:
 	mutex_unlock(&mdevice->devmem_lock);
+	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
+err_devmem:
+	kfree(devmem);
+
 	return false;
 }
 
_

Patches currently in -mm which might be from dan.carpenter@oracle.com are

mm-memremap_pages-convert-to-struct-range-fix.patch