mm: bootmem: fix free_all_bootmem_core() with odd bitmap alignment

jcmvbkbc · torvalds · commit 10d73e655cef · 2013-01-11T14:54:55.000-08:00
Currently free_all_bootmem_core ignores that node_min_pfn may be not multiple of BITS_PER_LONG. Eg commit 6dccdcb ("mm: bootmem: fix checking the bitmap when finally freeing bootmem") shifts vec by lower bits of start instead of lower bits of idx. Also if (IS_ALIGNED(start, BITS_PER_LONG) && vec == ~0UL) assumes that vec bit 0 corresponds to start pfn, which is only true when node_min_pfn is a multiple of BITS_PER_LONG. Also loop in the else clause can double-free pages (e.g. with node_min_pfn == start == 1, map[0] == ~0 on 32-bit machine page 32 will be double-freed). This bug causes the following message during xtensa kernel boot: bootmem::free_all_bootmem_core nid=0 start=1 end=8000 BUG: Bad page state in process swapper pfn:00001 page:d04bd020 count:0 mapcount:-127 mapping: (null) index:0x2 page flags: 0x0() Call Trace: bad_page+0x8c/0x9c free_pages_prepare+0x5e/0x88 free_hot_cold_page+0xc/0xa0 __free_pages+0x24/0x38 __free_pages_bootmem+0x54/0x56 free_all_bootmem_core$part$11+0xeb/0x138 free_all_bootmem+0x46/0x58 mem_init+0x25/0xa4 start_kernel+0x11e/0x25c should_never_return+0x0/0x3be7 The fix is the following: - always align vec so that its bit 0 corresponds to start - provide BITS_PER_LONG bits in vec, if those bits are available in the map - don't free pages past next start position in the else clause. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> Cc: Gavin Shan <shangw@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tejun Heo <tj@kernel.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Joonsoo Kim <js1304@gmail.com> Cc: Prasad Koya <prasad.koya@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/bootmem.c b/mm/bootmem.c
@@ -185,10 +185,23 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 
 	while (start < end) {
 		unsigned long *map, idx, vec;
+		unsigned shift;
 
 		map = bdata->node_bootmem_map;
 		idx = start - bdata->node_min_pfn;
+		shift = idx & (BITS_PER_LONG - 1);
+		/*
+		 * vec holds at most BITS_PER_LONG map bits,
+		 * bit 0 corresponds to start.
+		 */
 		vec = ~map[idx / BITS_PER_LONG];
+
+		if (shift) {
+			vec >>= shift;
+			if (end - start >= BITS_PER_LONG)
+				vec |= ~map[idx / BITS_PER_LONG + 1] <<
+					(BITS_PER_LONG - shift);
+		}
 		/*
 		 * If we have a properly aligned and fully unreserved
 		 * BITS_PER_LONG block of pages in front of us, free
@@ -201,19 +214,18 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 			count += BITS_PER_LONG;
 			start += BITS_PER_LONG;
 		} else {
-			unsigned long off = 0;
+			unsigned long cur = start;
 
-			vec >>= start & (BITS_PER_LONG - 1);
-			while (vec) {
+			start = ALIGN(start + 1, BITS_PER_LONG);
+			while (vec && cur != start) {
 				if (vec & 1) {
-					page = pfn_to_page(start + off);
+					page = pfn_to_page(cur);
 					__free_pages_bootmem(page, 0);
 					count++;
 				}
 				vec >>= 1;
-				off++;
+				++cur;
 			}
-			start = ALIGN(start + 1, BITS_PER_LONG);
 		}
 	}
 
