| From 77e6daad36eca743a853370acb43690c73bf02e5 Mon Sep 17 00:00:00 2001 |
| From: Qian Cai <cai@lca.pw> |
| Date: Sun, 6 Oct 2019 17:58:25 -0700 |
| Subject: [PATCH] mm/page_alloc.c: fix a crash in free_pages_prepare() |
| |
| commit 234fdce892f905cbc2674349a9eb4873e288e5b3 upstream. |
| |
| 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 |
| |
| In the past, only kernel_poison_pages() would trigger this but it needs |
| "page_poison=on" kernel cmdline, and I suspect nobody tested that on |
| s390. Recently, kernel_init_free_pages() (commit 6471384af2a6 ("mm: |
| security: introduce init_on_alloc=1 and init_on_free=1 boot options")) |
| was added and could trigger this as well. |
| |
| [akpm@linux-foundation.org: add comment] |
| Link: http://lkml.kernel.org/r/1569613623-16820-1-git-send-email-cai@lca.pw |
| Fixes: 8823b1dbc05f ("mm/page_poison.c: enable PAGE_POISONING as a separate option") |
| Fixes: 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options") |
| Signed-off-by: Qian Cai <cai@lca.pw> |
| Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> |
| Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> |
| Acked-by: Michal Hocko <mhocko@suse.com> |
| Cc: "Kirill A. Shutemov" <kirill@shutemov.name> |
| Cc: Vasily Gorbik <gor@linux.ibm.com> |
| Cc: Alexander Duyck <alexander.duyck@gmail.com> |
| Cc: <stable@vger.kernel.org> [5.3+] |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/mm/page_alloc.c b/mm/page_alloc.c |
| index 81177ed87a38..8b6a295fdb02 100644 |
| --- a/mm/page_alloc.c |
| +++ b/mm/page_alloc.c |
| @@ -1140,8 +1140,14 @@ 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); |
| kernel_poison_pages(page, 1 << order, 0); |
| + /* |
| + * arch_free_page() can make the page's contents inaccessible. s390 |
| + * does this. So nothing which can access the page's contents should |
| + * happen after this. |
| + */ |
| + arch_free_page(page, order); |
| + |
| if (debug_pagealloc_enabled()) |
| kernel_map_pages(page, 1 << order, 0); |
| |
| -- |
| 2.7.4 |
| |
