Patchwork [3.5.y.z,extended,stable] Patch "mm: bootmem: fix free_all_bootmem_core() with odd bitmap" has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Jan. 23, 2013, 4:44 a.m.
Message ID <1358916254-24185-1-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/214967/
State New
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Herton Ronaldo Krzesinski - Jan. 23, 2013, 4:44 a.m.
This is a note to let you know that I have just added a patch titled

    mm: bootmem: fix free_all_bootmem_core() with odd bitmap

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

From 8e28c901ec154617d21dcc463b0a7e11b69912ca Mon Sep 17 00:00:00 2001
From: Max Filippov <jcmvbkbc@gmail.com>
Date: Fri, 11 Jan 2013 14:31:52 -0800
Subject: [PATCH] mm: bootmem: fix free_all_bootmem_core() with odd bitmap
 alignment

commit 10d73e655cef6e86ea8589dca3df4e495e4900b0 upstream.

Currently free_all_bootmem_core ignores that node_min_pfn may be not
multiple of BITS_PER_LONG.  Eg commit 6dccdcbe2c3e ("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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 mm/bootmem.c |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

--
1.7.9.5

Patch

diff --git a/mm/bootmem.c b/mm/bootmem.c
index bcb63ac..ceca0da 100644
--- 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);
 		}
 	}