[patch 069/134] mm/sparse.c: fix memory leak of sparsemap_buf in aligned memory

[akpm@xxxxxxxxxxxxxxxxxxxx]

From: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Subject: mm/sparse.c: fix memory leak of sparsemap_buf in aligned memory

sparse_buffer_alloc(xsize) gets the size of memory from sparsemap_buf
after being aligned with the size.  However, the size is at least
PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION) and usually larger
than PAGE_SIZE.

Also, sparse_buffer_fini() only frees memory between sparsemap_buf and
sparsemap_buf_end, since sparsemap_buf may be changed by PTR_ALIGN()
first, the aligned space before sparsemap_buf is wasted and no one will
touch it.

In our ARM32 platform (without SPARSEMEM_VMEMMAP)
  Sparse_buffer_init
    Reserve d359c000 - d3e9c000 (9M)
  Sparse_buffer_alloc
    Alloc   d3a00000 - d3E80000 (4.5M)
  Sparse_buffer_fini
    Free    d3e80000 - d3e9c000 (~=100k)
 The reserved memory between d359c000 - d3a00000 (~=4.4M) is unfreed.

In ARM64 platform (with SPARSEMEM_VMEMMAP)

  sparse_buffer_init
    Reserve ffffffc07d623000 - ffffffc07f623000 (32M)
  Sparse_buffer_alloc
    Alloc   ffffffc07d800000 - ffffffc07f600000 (30M)
  Sparse_buffer_fini
    Free    ffffffc07f600000 - ffffffc07f623000 (140K)
 The reserved memory between ffffffc07d623000 - ffffffc07d800000
 (~=1.9M) is unfreed.

Let's explicit free redundant aligned memory.

[arnd@xxxxxxxx: mark sparse_buffer_free as __meminit]
  Link: http://lkml.kernel.org/r/20190709185528.3251709-1-arnd@xxxxxxxx
Link: http://lkml.kernel.org/r/20190705114730.28534-1-lecopzer.chen@xxxxxxxxxxxx
Signed-off-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Signed-off-by: Mark-PK Tsai <Mark-PK.Tsai@xxxxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: YJ Chiang <yj.chiang@xxxxxxxxxxxx>
Cc: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/sparse.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/mm/sparse.c~mm-sparse-fix-memory-leak-of-sparsemap_buf-in-aliged-memory
+++ a/mm/sparse.c
@@ -470,6 +470,12 @@ struct page __init *__populate_section_m
 static void *sparsemap_buf __meminitdata;
 static void *sparsemap_buf_end __meminitdata;
 
+static inline void __meminit sparse_buffer_free(unsigned long size)
+{
+	WARN_ON(!sparsemap_buf || size == 0);
+	memblock_free_early(__pa(sparsemap_buf), size);
+}
+
 static void __init sparse_buffer_init(unsigned long size, int nid)
 {
 	phys_addr_t addr = __pa(MAX_DMA_ADDRESS);
@@ -486,7 +492,7 @@ static void __init sparse_buffer_fini(vo
 	unsigned long size = sparsemap_buf_end - sparsemap_buf;
 
 	if (sparsemap_buf && size > 0)
-		memblock_free_early(__pa(sparsemap_buf), size);
+		sparse_buffer_free(size);
 	sparsemap_buf = NULL;
 }
 
@@ -498,8 +504,12 @@ void * __meminit sparse_buffer_alloc(uns
 		ptr = PTR_ALIGN(sparsemap_buf, size);
 		if (ptr + size > sparsemap_buf_end)
 			ptr = NULL;
-		else
+		else {
+			/* Free redundant aligned space */
+			if ((unsigned long)(ptr - sparsemap_buf) > 0)
+				sparse_buffer_free((unsigned long)(ptr - sparsemap_buf));
 			sparsemap_buf = ptr + size;
+		}
 	}
 	return ptr;
 }
_