Currently free_all_bootmem_core ignores that node_min_pfn may be not
multiple of BITS_PER_LONG. E.g. commit 6dccdcbe "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:
[ 0.000000] bootmem::free_all_bootmem_core nid=0 start=1 end=8000
[ 0.000000] BUG: Bad page state in process swapper pfn:00001
[ 0.000000] page:d04bd020 count:0 mapcount:-127 mapping: (null) index:0x2
[ 0.000000] page flags: 0x0()
[ 0.000000]
[ 0.000000] Stack: 00000000 00000002 00000004 ffffffff d0193e44 ffffff81 00000000 00000002
[ 0.000000] 90038c66 d0193e90 d04bd020 000001a8 00000000 ffffffff 00000000 00000020
[ 0.000000] 90039a4c d0193eb0 d04bd020 00000001 d04b7b20 ffff8ad0 00000000 00000000
[ 0.000000] Call Trace:
[ 0.000000] [<d0038bf8>] bad_page+0x8c/0x9c
[ 0.000000] [<d0038c66>] free_pages_prepare+0x5e/0x88
[ 0.000000] [<d0039a4c>] free_hot_cold_page+0xc/0xa0
[ 0.000000] [<d0039b28>] __free_pages+0x24/0x38
[ 0.000000] [<d01b8230>] __free_pages_bootmem+0x54/0x56
[ 0.000000] [<d01b1667>] free_all_bootmem_core$part$11+0xeb/0x138
[ 0.000000] [<d01b179e>] free_all_bootmem+0x46/0x58
[ 0.000000] [<d01ae7a9>] mem_init+0x25/0xa4
[ 0.000000] [<d01ad13e>] start_kernel+0x11e/0x25c
[ 0.000000] [<d01a9121>] 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@xxxxxxxxx>
---
Sent wrong version for v1, 'while' should have been 'for'.
mm/bootmem.c | 23 +++++++++++++++++------
1 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/mm/bootmem.c b/mm/bootmem.c
index 1324cd7..1157be7 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 +214,17 @@ 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;
- vec >>= start & (BITS_PER_LONG - 1);
- while (vec) {
+ start = ALIGN(start + 1, BITS_PER_LONG);
+ for (cur = start; vec && cur != start; ++cur) {
if (vec & 1) {
- page = pfn_to_page(start + off);
+ page = pfn_to_page(cur);
__free_pages_bootmem(page, 0);
count++;
}
vec >>= 1;
- off++;
}
- start = ALIGN(start + 1, BITS_PER_LONG);
}
}
--
1.7.7.6
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