Since a few days ago, s390 starts to crash on linux-next while reading some sysfs. It is not always reproducible but seems pretty reproducible after running the whole MM test suite here, https://github.com/cailca/linux-mm/blob/master/test.sh the config: https://raw.githubusercontent.com/cailca/linux-mm/master/s390.config The stack trace on s390 is not particular helpful as both gdb and faddr2line are unable to point out which line causes the issue. # ./scripts/faddr2line vmlinux collect_percpu_times+0x2d6/0x798 bad symbol size: base: 0x00000000002076f8 end: 0x00000000002076f8 (gdb) list *(collect_percpu_times+0x2d6) 0x2079ce is in collect_percpu_times (./include/linux/compiler.h:199). 194 }) 195 196 static __always_inline 197 void __read_once_size(const volatile void *p, void *res, int size) 198 { 199 __READ_ONCE_SIZE; 200 } 201 202 #ifdef CONFIG_KASAN 203 /* Could it be some race conditions in PSI? 01: [ 9499.451788] LTP: starting read_all_sys (read_all -d /sys -q -r 10) (zcon 17:55:45) [-- MARK --] 00: [ 9777.709470] ============================================================= 00: ===== 00: [ 9777.709515] BUG: KASAN: use-after-free in collect_percpu_times+0x2d6/0x79 00: 8 00: [ 9777.709530] Read of size 4 at addr 0000000066229000 by task read_all/5024 00: 0 00: [ 9777.709543] 00: [ 9777.709559] CPU: 0 PID: 50240 Comm: read_all Not tainted 5.4.0-rc7-next-2 00: 0191118 #4 00: [ 9777.709573] Hardware name: IBM 2964 N96 400 (z/VM 6.4.0) 00: [ 9777.709586] Call Trace: 00: [ 9777.709604] ([<000000000568e202>] show_stack+0x11a/0x1b8) 00: [ 9777.709624] [<0000000005f7568e>] dump_stack+0x136/0x188 00: [ 9777.709641] [<0000000005a16594>] print_address_description.isra.8+0x64/0 00: x3f0 00: [ 9777.709657] [<0000000005a16b6a>] __kasan_report+0x162/0x188 00: [ 9777.709672] [<00000000057779ce>] collect_percpu_times+0x2d6/0x798 00: [ 9777.709687] [<000000000577a10c>] psi_show+0x84/0x2b0 00: [ 9777.709703] [<0000000005abf18c>] seq_read+0x2b4/0x838 00: [ 9777.709718] [<0000000005a75502>] vfs_read+0x9a/0x158 00: [ 9777.709732] [<0000000005a759ea>] ksys_read+0xea/0x190 00: [ 9777.709748] [<0000000005fb3100>] system_call+0xd8/0x2b4 00: [ 9777.709759] INFO: lockdep is turned off. 00: [ 9777.709769] 00: [ 9777.709778] The buggy address belongs to the page: 00: [ 9777.709793] page:000003d081988a40 refcount:0 mapcount:-2048 mapping:00000 00: 00000000000 index:0x0 00: [ 9777.709813] raw: 003fffc000000000 000003d081988a48 000003d081988a48 00000 00: 00000000000 00: [ 9777.709831] raw: 0000000000000000 0000000000000000 fffff7ff00000000 00000 00: 00000000000 00: [ 9777.710042] page dumped because: kasan: bad access detected 00: [ 9777.710057] page_owner tracks the page as freed 00: [ 9777.710075] page last allocated via order 2, migratetype Unmovable, gfp_m 00: ask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP) 00: [ 9777.710145] stack_trace_save+0xc2/0xd8 00: [ 9777.710158] register_dummy_stack+0x94/0xc0 00: [ 9777.710170] init_page_owner+0x5c/0x518 00: [ 9777.710188] kernel_init_freeable+0x2a4/0x5a8 00: [ 9777.710199] page last free stack trace: 00: [ 9777.710212] stack_trace_save+0xc2/0xd8 00: [ 9777.710224] register_dummy_stack+0x94/0xc0 00: [ 9777.710236] init_page_owner+0x5c/0x518 00: [ 9777.710249] kernel_init_freeable+0x2a4/0x5a8 00: [ 9777.710259] 00: [ 9777.710267] Memory state around the buggy address: 00: [ 9777.710282] 0000000066228f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc 00: fc fc 00: [ 9777.710297] 0000000066228f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc 00: fc fc 00: [ 9777.710312] >0000000066229000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00: ff ff 00: [ 9777.710325] ^ 00: [ 9777.710337] 0000000066229080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00: ff ff 00: [ 9777.710352] 0000000066229100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00: ff ff 00: [ 9777.710366] ============================================================= 00: ===== 00: [ 9777.710389] Unable to handle kernel pointer dereference in virtual kernel 00: address space 00: [ 9777.710580] Failing address: 0000000066229000 TEID: 0000000066229803 00: [ 9777.710595] Fault in home space mode while using kernel ASCE. 00: [ 9777.710613] AS:0000000007084007 R3:000000006dc28007 S:000000006d8fa800 P: 00: 000000006622943d 00: [ 9777.710700] Oops: 0011 ilc:2 [#1] SMP DEBUG_PAGEALLOC 00: [ 9777.710719] Modules linked in: brd ext4 crc16 mbcache jbd2 loop ip_tables 00: x_tables xfs dasd_fba_mod dasd_eckd_mod dm_mirror dm_region_hash dm_log dm_ 00: mod 00: [ 9777.710778] CPU: 0 PID: 50240 Comm: read_all Tainted: G B 00: 5.4.0-rc7-next-20191118 #4 00: [ 9777.710794] Hardware name: IBM 2964 N96 400 (z/VM 6.4.0) 00: [ 9777.710806] Krnl PSW : 0704c00180000000 00000000057779ce (collect_percpu_ 00: times+0x2d6/0x798) 00: [ 9777.710832] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 00: RI:0 EA:3 00: [ 9777.710849] Krnl GPRS: 0000000000000001 000000004a8b2100 00000000063315ac 00: 0000000000000007 00: [ 9777.710865] 0000030000000000 000000000578e0be 0000000000000001 00: 000000003409fc70 00: [ 9777.710881] 000000000577a10c 070000003409fb00 0000000066229008 00: 0000000066229000 00: [ 9777.710896] 000000000639f6b0 0000000005ff5d30 00000000057779ce 00: 000000003409fa20 00: [ 9777.710939] Krnl Code: 00000000057779c0: ad031000 stosm 0(%r 00: 1),3 00: [ 9777.710939] 00000000057779c4: b904002b lgr %r2, 00: %r11 00: [ 9777.710939] #00000000057779c8: c0e50014fc9c brasl %r14 00: ,0000000005a17300 00: [ 9777.710939] >00000000057779ce: 5880b000 l %r8, 00: 0(%r11) 00: [ 9777.710939] 00000000057779d2: a7810001 tmll %r8, 00: 1 00: [ 9777.710939] 00000000057779d6: a784ff97 brc 8,00 00: 00000005777904 00: [ 9777.710939] 00000000057779da: a7f4ff8a brc 15,0 00: 0000000057778ee 00: [ 9777.710939] 00000000057779de: e310f1300004 lg %r1, 00: 304(%r15) 00: [ 9777.711135] Call Trace: 00: [ 9777.711149] ([<00000000057779ce>] collect_percpu_times+0x2d6/0x798) 00: [ 9777.711164] [<000000000577a10c>] psi_show+0x84/0x2b0 00: [ 9777.711180] [<0000000005abf18c>] seq_read+0x2b4/0x838 00: [ 9777.711194] [<0000000005a75502>] vfs_read+0x9a/0x158 00: [ 9777.711207] [<0000000005a759ea>] ksys_read+0xea/0x190 00: [ 9777.711222] [<0000000005fb3100>] system_call+0xd8/0x2b4 00: [ 9777.711234] INFO: lockdep is turned off. 00: [ 9777.711244] Last Breaking-Event-Address: 00: [ 9777.711257] [<0000000005a16a70>] __kasan_report+0x68/0x188 00: [ 9777.711273] Kernel panic - not syncing: Fatal exception: panic_on_oops
