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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id c202sm58098647qkb.19.2019.01.21.12.04.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 21 Jan 2019 12:04:53 -0800 (PST) From: Qian Cai To: akpm@linux-foundation.org Cc: osalvador@suse.de, catalin.marinas@arm.com, vbabka@suse.cz, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH v2] mm/hotplug: invalid PFNs from pfn_to_online_page() Date: Mon, 21 Jan 2019 15:04:35 -0500 Message-Id: <20190121200435.22488-1-cai@lca.pw> X-Mailer: git-send-email 2.17.2 (Apple Git-113) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On an arm64 ThunderX2 server, the first kmemleak scan would crash [1] with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is not directly mapped (MEMBLOCK_NOMAP). Hence, the page->flags is uninitialized. This is due to the commit 9f1eb38e0e11 ("mm, kmemleak: little optimization while scanning") starts to use pfn_to_online_page() instead of pfn_valid(). However, in the CONFIG_MEMORY_HOTPLUG=y case, pfn_to_online_page() does not call memblock_is_map_memory() while pfn_valid() does. Historically, the commit 68709f45385a ("arm64: only consider memblocks with NOMAP cleared for linear mapping") causes pages marked as nomap being no long reassigned to the new zone in memmap_init_zone() by calling __init_single_page(). Since the commit 2d070eab2e82 ("mm: consider zone which is not fully populated to have holes") introduced pfn_to_online_page() and was designed to return a valid pfn only, but it is clearly broken on arm64. Therefore, let pfn_to_online_page() calls pfn_valid_within(), so it can handle nomap thanks to the commit f52bb98f5ade ("arm64: mm: always enable CONFIG_HOLES_IN_ZONE"), while it will be optimized away on architectures where have no HOLES_IN_ZONE. [1] [ 102.195320] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000006 [ 102.204113] Mem abort info: [ 102.206921] ESR = 0x96000005 [ 102.209997] Exception class = DABT (current EL), IL = 32 bits [ 102.215926] SET = 0, FnV = 0 [ 102.218993] EA = 0, S1PTW = 0 [ 102.222150] Data abort info: [ 102.225047] ISV = 0, ISS = 0x00000005 [ 102.228887] CM = 0, WnR = 0 [ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____) [ 102.238572] [0000000000000006] pgd=0000000000000000, pud=0000000000000000 [ 102.245448] Internal error: Oops: 96000005 [#1] SMP [ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8 [ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO) [ 102.280409] pc : page_mapping+0x24/0x144 [ 102.280415] lr : __dump_page+0x34/0x3dc [ 102.292923] sp : ffff00003a5cfd10 [ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f [ 102.301533] x27: 0000000000000000 x26: 0000000000277d00 [ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000 [ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670 [ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b [ 102.322747] x19: fffffffffffffffe x18: 0000000000000000 [ 102.328049] x17: 0000000000000000 x16: 0000000000000000 [ 102.333352] x15: 0000000000000000 x14: ffff802698b19600 [ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00 [ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400 [ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000 [ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8 [ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003 [ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000 [ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff [ 102.375782] Process kmemleak (pid: 1408, stack limit = 0x(____ptrval____)) [ 102.382648] Call trace: [ 102.385091] page_mapping+0x24/0x144 [ 102.388659] __dump_page+0x34/0x3dc [ 102.392140] dump_page+0x28/0x4c [ 102.395363] kmemleak_scan+0x4ac/0x680 [ 102.399106] kmemleak_scan_thread+0xb4/0xdc [ 102.403285] kthread+0x12c/0x13c [ 102.406509] ret_from_fork+0x10/0x18 [ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661) [ 102.416357] ---[ end trace 4d4bd7f573490c8e ]--- [ 102.420966] Kernel panic - not syncing: Fatal exception [ 102.426293] SMP: stopping secondary CPUs [ 102.431830] Kernel Offset: disabled [ 102.435311] CPU features: 0x002,20000c38 [ 102.439223] Memory Limit: none [ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]--- Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to have holes") Signed-off-by: Qian Cai --- v2: update the changelog; keep the bound check; use pfn_valid_within(). include/linux/memory_hotplug.h | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 07da5c6c5ba0..cdeecd9bd87e 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -21,14 +21,15 @@ struct vmem_altmap; * walkers which rely on the fully initialized page->flags and others * should use this rather than pfn_valid && pfn_to_page */ -#define pfn_to_online_page(pfn) \ -({ \ - struct page *___page = NULL; \ - unsigned long ___nr = pfn_to_section_nr(pfn); \ - \ - if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr))\ - ___page = pfn_to_page(pfn); \ - ___page; \ +#define pfn_to_online_page(pfn) \ +({ \ + struct page *___page = NULL; \ + unsigned long ___nr = pfn_to_section_nr(pfn); \ + \ + if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr) && \ + pfn_valid_within(pfn)) \ + ___page = pfn_to_page(pfn); \ + ___page; \ }) /* -- 2.17.2 (Apple Git-113)