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| author | Hui Zhu <zhuhui@xiaomi.com> | 2015-05-14 15:17:04 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-05-14 17:55:51 -0700 |
| commit | 1ae7013dfa4281644a9a9591105c24d639216b22 (patch) | |
| tree | e4f5330d417ec38a9389e9fed56efdce86635bb7 /mm/page_isolation.c | |
| parent | 929aa5b250bfc59aca492d3213c7f3a53e2a5247 (diff) | |
| download | lwn-1ae7013dfa4281644a9a9591105c24d639216b22.tar.gz lwn-1ae7013dfa4281644a9a9591105c24d639216b22.zip | |
CMA: page_isolation: check buddy before accessing it
I had an issue:
Unable to handle kernel NULL pointer dereference at virtual address 0000082a
pgd = cc970000
[0000082a] *pgd=00000000
Internal error: Oops: 5 [#1] PREEMPT SMP ARM
PC is at get_pageblock_flags_group+0x5c/0xb0
LR is at unset_migratetype_isolate+0x148/0x1b0
pc : [<c00cc9a0>] lr : [<c0109874>] psr: 80000093
sp : c7029d00 ip : 00000105 fp : c7029d1c
r10: 00000001 r9 : 0000000a r8 : 00000004
r7 : 60000013 r6 : 000000a4 r5 : c0a357e4 r4 : 00000000
r3 : 00000826 r2 : 00000002 r1 : 00000000 r0 : 0000003f
Flags: Nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user
Control: 10c5387d Table: 2cb7006a DAC: 00000015
Backtrace:
get_pageblock_flags_group+0x0/0xb0
unset_migratetype_isolate+0x0/0x1b0
undo_isolate_page_range+0x0/0xdc
__alloc_contig_range+0x0/0x34c
alloc_contig_range+0x0/0x18
This issue is because when calling unset_migratetype_isolate() to unset
a part of CMA memory, it try to access the buddy page to get its status:
if (order >= pageblock_order) {
page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
buddy_idx = __find_buddy_index(page_idx, order);
buddy = page + (buddy_idx - page_idx);
if (!is_migrate_isolate_page(buddy)) {
But the begin addr of this part of CMA memory is very close to a part of
memory that is reserved at boot time (not in buddy system). So add a
check before accessing it.
[akpm@linux-foundation.org: use conventional code layout]
Signed-off-by: Hui Zhu <zhuhui@xiaomi.com>
Suggested-by: Laura Abbott <labbott@redhat.com>
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_isolation.c')
| -rw-r--r-- | mm/page_isolation.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 755a42c76eb4..303c908790ef 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -101,7 +101,8 @@ void unset_migratetype_isolate(struct page *page, unsigned migratetype) buddy_idx = __find_buddy_index(page_idx, order); buddy = page + (buddy_idx - page_idx); - if (!is_migrate_isolate_page(buddy)) { + if (pfn_valid_within(page_to_pfn(buddy)) && + !is_migrate_isolate_page(buddy)) { __isolate_free_page(page, order); kernel_map_pages(page, (1 << order), 1); set_page_refcounted(page); |