CVE-2023-52739

In the Linux kernel, the following vulnerability has been resolved:

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.