• D
    Fix page corruption caused by racy check in __free_pages · 462a8e08
    David Chen 提交于
    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
    e320d301 ("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: e320d301 ("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: NChunwei Chen <david.chen@nutanix.com>
    Reviewed-by: NVlastimil Babka <vbabka@suse.cz>
    Reviewed-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    462a8e08
page_alloc.c 269.8 KB