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authorDavid Chen <david.chen@nutanix.com>2023-02-09 17:48:28 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2023-02-12 10:30:05 -0800
commit462a8e08e0e6287e5ce13187257edbf24213ed03 (patch)
treec217d58ec11f8d69b26071e3b440821bbf715464
parentf339c2597ebb00e738f2b6328c14804ed19f5d57 (diff)
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Fix page corruption caused by racy check in __free_pages
When we upgraded our kernel, we started seeing some page corruption like the following consistently: BUG: Bad page state in process ganesha.nfsd pfn:1304ca page:0000000022261c55 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x1304ca flags: 0x17ffffc0000000() raw: 0017ffffc0000000 ffff8a513ffd4c98 ffffeee24b35ec08 0000000000000000 raw: 0000000000000000 0000000000000001 00000000ffffff7f 0000000000000000 page dumped because: nonzero mapcount CPU: 0 PID: 15567 Comm: ganesha.nfsd Kdump: loaded Tainted: P B O 5.10.158-1.nutanix.20221209.el7.x86_64 #1 Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/05/2016 Call Trace: dump_stack+0x74/0x96 bad_page.cold+0x63/0x94 check_new_page_bad+0x6d/0x80 rmqueue+0x46e/0x970 get_page_from_freelist+0xcb/0x3f0 ? _cond_resched+0x19/0x40 __alloc_pages_nodemask+0x164/0x300 alloc_pages_current+0x87/0xf0 skb_page_frag_refill+0x84/0x110 ... Sometimes, it would also show up as corruption in the free list pointer and cause crashes. After bisecting the issue, we found the issue started from commit e320d3012d25 ("mm/page_alloc.c: fix freeing non-compound pages"): if (put_page_testzero(page)) free_the_page(page, order); else if (!PageHead(page)) while (order-- > 0) free_the_page(page + (1 << order), order); So the problem is the check PageHead is racy because at this point we already dropped our reference to the page. So even if we came in with compound page, the page can already be freed and PageHead can return false and we will end up freeing all the tail pages causing double free. Fixes: e320d3012d25 ("mm/page_alloc.c: fix freeing non-compound pages") Link: https://lore.kernel.org/lkml/BYAPR02MB448855960A9656EEA81141FC94D99@BYAPR02MB4488.namprd02.prod.outlook.com/ Cc: Andrew Morton <akpm@linux-foundation.org> Cc: stable@vger.kernel.org Signed-off-by: Chunwei Chen <david.chen@nutanix.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0745aedebb37..3bb3484563ed 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5631,9 +5631,12 @@ EXPORT_SYMBOL(get_zeroed_page);
*/
void __free_pages(struct page *page, unsigned int order)
{
+ /* get PageHead before we drop reference */
+ int head = PageHead(page);
+
if (put_page_testzero(page))
free_the_page(page, order);
- else if (!PageHead(page))
+ else if (!head)
while (order-- > 0)
free_the_page(page + (1 << order), order);
}