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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id 44sm3980781qtt.13.2019.09.27.12.47.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 Sep 2019 12:47:33 -0700 (PDT) From: Qian Cai To: akpm@linux-foundation.org Cc: heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] mm/page_alloc: fix a crash in free_pages_prepare() Date: Fri, 27 Sep 2019 15:47:03 -0400 Message-Id: <1569613623-16820-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.010040, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On architectures like s390, arch_free_page() could mark the page unused (set_page_unused()) and any access later would trigger a kernel panic. Fix it by moving arch_free_page() after all possible accessing calls. Hardware name: IBM 2964 N96 400 (z/VM 6.4.0) Krnl PSW : 0404e00180000000 0000000026c2b96e (__free_pages_ok+0x34e/0x5d8) R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000088d43af7 0000000000484000 000000000000007c 000000000000000f 000003d080012100 000003d080013fc0 0000000000000000 0000000000100000 00000000275cca48 0000000000000100 0000000000000008 000003d080010000 00000000000001d0 000003d000000000 0000000026c2b78a 000000002717fdb0 Krnl Code: 0000000026c2b95c: ec1100b30659 risbgn %r1,%r1,0,179,6 0000000026c2b962: e32014000036 pfd 2,1024(%r1) #0000000026c2b968: d7ff10001000 xc 0(256,%r1),0(%r1) >0000000026c2b96e: 41101100 la %r1,256(%r1) 0000000026c2b972: a737fff8 brctg %r3,26c2b962 0000000026c2b976: d7ff10001000 xc 0(256,%r1),0(%r1) 0000000026c2b97c: e31003400004 lg %r1,832 0000000026c2b982: ebff1430016a asi 5168(%r1),-1 Call Trace: __free_pages_ok+0x16a/0x5d8) memblock_free_all+0x206/0x290 mem_init+0x58/0x120 start_kernel+0x2b0/0x570 startup_continue+0x6a/0xc0 INFO: lockdep is turned off. Last Breaking-Event-Address: __free_pages_ok+0x372/0x5d8 Kernel panic - not syncing: Fatal exception: panic_on_oops 00: HCPGIR450W CP entered; disabled wait PSW 00020001 80000000 00000000 26A2379C Signed-off-by: Qian Cai Reviewed-by: Heiko Carstens Acked-by: Michal Hocko --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3334a769eb91..a54ff6a60649 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1175,11 +1175,11 @@ static __always_inline bool free_pages_prepare(struct page *page, debug_check_no_obj_freed(page_address(page), PAGE_SIZE << order); } - arch_free_page(page, order); if (want_init_on_free()) kernel_init_free_pages(page, 1 << order); kernel_poison_pages(page, 1 << order, 0); + arch_free_page(page, order); if (debug_pagealloc_enabled()) kernel_map_pages(page, 1 << order, 0);