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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=MhemdCQE; spf=none (imf25.hostedemail.com: domain of apopple@nvidia.com has no SPF policy when checking 40.107.95.57) smtp.mailfrom=apopple@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com X-Stat-Signature: xsebjaocsqknmapwxnpk4q7enru48a44 X-Rspamd-Server: rspam11 X-HE-Tag: 1644893927-471828 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: ZONE_MOVABLE uses the remaining memory in each node. It's starting pfn is also aligned to MAX_ORDER_NR_PAGES. It is possible for the remaining memory in a node to be less than MAX_ORDER_NR_PAGES, meaning there is not enough room for ZONE_MOVABLE on that node. Unfortunately this condition is not checked for. This leads to zone_movable_pfn[] getting set to a pfn greater than the last pfn in a node. calculate_node_totalpages() then sets zone->present_pages to be greater than zone->spanned_pages which is invalid, as spanned_pages represents the maximum number of pages in a zone assuming no holes. Subsequently it is possible free_area_init_core() will observe a zone of size zero with present pages. In this case it will skip setting up the zone, including the initialisation of free_lists[]. However populated_zone() checks zone->present_pages to see if a zone has memory available. This is used by iterators such as walk_zones_in_node(). pagetypeinfo_showfree() uses this to walk the free_list of each zone in each node, which are assumed to be initialised due to the zone not being empty. As free_area_init_core() never initialised the free_lists[] this results in the following kernel crash when trying to read /proc/pagetypeinfo: [ 67.534914] BUG: kernel NULL pointer dereference, address: 00000000000= 00000 [ 67.535429] #PF: supervisor read access in kernel mode [ 67.535789] #PF: error_code(0x0000) - not-present page [ 67.536128] PGD 0 P4D 0 [ 67.536305] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI [ 67.536696] CPU: 0 PID: 456 Comm: cat Not tainted 5.16.0 #461 [ 67.537096] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1= .14.0-2 04/01/2014 [ 67.537638] RIP: 0010:pagetypeinfo_show+0x163/0x460 [ 67.537992] Code: 9e 82 e8 80 57 0e 00 49 8b 06 b9 01 00 00 00 4c 39 f= 0 75 16 e9 65 02 00 00 48 83 c1 01 48 81 f9 a0 86 01 00 0f 84 48 02 00 00= <48> 8b 00 4c 39 f0 75 e7 48 c7 c2 80 a2 e2 82 48 c7 c6 79 ef e3 82 [ 67.538259] RSP: 0018:ffffc90001c4bd10 EFLAGS: 00010003 [ 67.538259] RAX: 0000000000000000 RBX: ffff88801105f638 RCX: 000000000= 0000001 [ 67.538259] RDX: 0000000000000001 RSI: 000000000000068b RDI: ffff88801= 63dc68b [ 67.538259] RBP: ffffc90001c4bd90 R08: 0000000000000001 R09: ffff88801= 63dc67e [ 67.538259] R10: 656c6261766f6d6e R11: 6c6261766f6d6e55 R12: ffff88807= ffb4a00 [ 67.538259] R13: ffff88807ffb49f8 R14: ffff88807ffb4580 R15: ffff88807= ffb3000 [ 67.538259] FS: 00007f9c83eff5c0(0000) GS:ffff88807dc00000(0000) knlG= S:0000000000000000 [ 67.538259] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 67.538259] CR2: 0000000000000000 CR3: 0000000013c8e000 CR4: 000000000= 0350ef0 [ 67.538259] Call Trace: [ 67.538259] [ 67.538259] seq_read_iter+0x128/0x460 [ 67.538259] ? aa_file_perm+0x1af/0x5f0 [ 67.538259] proc_reg_read_iter+0x51/0x80 [ 67.538259] ? lock_is_held_type+0xea/0x140 [ 67.538259] new_sync_read+0x113/0x1a0 [ 67.538259] vfs_read+0x136/0x1d0 [ 67.538259] ksys_read+0x70/0xf0 [ 67.538259] __x64_sys_read+0x1a/0x20 [ 67.538259] do_syscall_64+0x3b/0xc0 [ 67.538259] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 67.538259] RIP: 0033:0x7f9c83e23cce [ 67.538259] Code: c0 e9 b6 fe ff ff 50 48 8d 3d 6e 13 0a 00 e8 c9 e3 0= 1 00 66 0f 1f 84 00 00 00 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 0f 05= <48> 3d 00 f0 ff ff 77 5a c3 66 0f 1f 84 00 00 00 00 00 48 83 ec 28 [ 67.538259] RSP: 002b:00007fff116e1a08 EFLAGS: 00000246 ORIG_RAX: 0000= 000000000000 [ 67.538259] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f9c8= 3e23cce [ 67.538259] RDX: 0000000000020000 RSI: 00007f9c83a2c000 RDI: 000000000= 0000003 [ 67.538259] RBP: 00007f9c83a2c000 R08: 00007f9c83a2b010 R09: 000000000= 0000000 [ 67.538259] R10: 00007f9c83f2d7d0 R11: 0000000000000246 R12: 000000000= 0000000 [ 67.538259] R13: 0000000000000003 R14: 0000000000020000 R15: 000000000= 0020000 [ 67.538259] Fix this by checking that the aligned zone_movable_pfn[] does not exceed the end of the node, and if it does skip creating a movable zone on this node. Signed-off-by: Alistair Popple Fixes: 2a1e274acf0b ("Create the ZONE_MOVABLE zone") --- mm/page_alloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3589febc6d31..a1fbf656e7db 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7972,10 +7972,17 @@ static void __init find_zone_movable_pfns_for_nod= es(void) =20 out2: /* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */ - for (nid =3D 0; nid < MAX_NUMNODES; nid++) + for (nid =3D 0; nid < MAX_NUMNODES; nid++) { + unsigned long start_pfn, end_pfn; + zone_movable_pfn[nid] =3D roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES); =20 + get_pfn_range_for_nid(nid, &start_pfn, &end_pfn); + if (zone_movable_pfn[nid] >=3D end_pfn) + zone_movable_pfn[nid] =3D 0; + } + out: /* restore the node_state */ node_states[N_MEMORY] =3D saved_node_state; --=20 2.34.1