Re: [PATCH v4 09/10] eventfs: Move tracing/events to eventfs

Sven Schnelle
2023-09-08T12:14:57Z

Ajay Kaher <akaher@vmware.com> writes:

> Till now /sys/kernel/debug/tracing/events is a part of tracefs,
> with-in this patch creating 'events' and it's sub-dir as eventfs.
> Basically replacing tracefs calls with eventfs calls for 'events'.
>
> Signed-off-by: Ajay Kaher <akaher@vmware.com>
> Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> Tested-by: Ching-lin Yu <chinglinyu@google.com>
> ---
> fs/tracefs/inode.c | 18 ++++++++++
> include/linux/trace_events.h | 1 +
> kernel/trace/trace.h | 2 +-
> kernel/trace/trace_events.c | 67 +++++++++++++++++++-----------------
> 4 files changed, 55 insertions(+), 33 deletions(-)

With this patchset in next-20230908 the following crash is observed on
s390 while running ftracetest test.d/instances/instance-event.tc:

(It also crashes without KASAN, just not on every try)

[ 26.728436] ==================================================================
[ 26.728450] BUG: KASAN: slab-use-after-free in __ftrace_event_enable_disable+0x56c/0x648
[ 26.728460] Read of size 8 at addr 00000000107d3838 by task ftracetest/514
[ 26.728465]
[ 26.728468] CPU: 1 PID: 514 Comm: ftracetest Not tainted 6.5.0-rc4-00014-g27152bceea1d #958
[ 26.728474] Hardware name: IBM 3931 A01 704 (z/VM 7.3.0)
[ 26.728478] Call Trace:
[ 26.728482] [<000000000262349e>] dump_stack_lvl+0x106/0x1c8
[ 26.728490] [<00000000009e3b8c>] print_address_description.constprop.0+0x34/0x378
[ 26.728498] [<00000000009e3f7c>] print_report+0xac/0x240
[ 26.728504] [<00000000009e42fa>] kasan_report+0xf2/0x130
[ 26.728509] [<00000000005c61c4>] __ftrace_event_enable_disable+0x56c/0x648
[ 26.728516] [<00000000005c6d02>] event_enable_write+0x132/0x218
[ 26.728522] [<0000000000a89598>] vfs_write+0x208/0x930
[ 26.728528] [<0000000000a8a148>] ksys_write+0x118/0x200
[ 26.728535] [<000000000010c5fc>] do_syscall+0x22c/0x328
[ 26.728547] [<000000000268e8b2>] __do_syscall+0x9a/0xf8
[ 26.728553] [<00000000026c1d28>] system_call+0x70/0x98
[ 26.728559] 3 locks held by ftracetest/514:
[ 26.728562] #0: 00000000226addd8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x84/0xa0
[ 26.728577] #1: 0000000008f19440 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x118/0x200
[ 26.728594] #2: 00000000033205d0 (event_mutex){+.+.}-{3:3}, at: event_enable_write+0xdc/0x218
[ 26.728609]
[ 26.728613] Allocated by task 515:
[ 26.728617] kasan_save_stack+0x40/0x68
[ 26.728627] kasan_set_track+0x36/0x48
[ 26.728632] __kasan_slab_alloc+0x8e/0xb8
[ 26.728638] kmem_cache_alloc+0x1ec/0x568
[ 26.728643] trace_create_new_event+0x88/0x3d8
[ 26.728648] event_trace_add_tracer+0x13a/0x2a0
[ 26.728654] trace_array_create_dir+0x80/0x1a0
[ 26.728660] trace_array_create+0x344/0x700
[ 26.728665] instance_mkdir+0xbe/0x118
[ 26.728670] tracefs_syscall_mkdir+0xa8/0xf8
[ 26.728678] vfs_mkdir+0x454/0x6c0
[ 26.728685] do_mkdirat+0x24e/0x2a8
[ 26.728692] __s390x_sys_mkdir+0xf4/0x168
[ 26.728696] do_syscall+0x22c/0x328
[ 26.728700] __do_syscall+0x9a/0xf8
[ 26.728704] system_call+0x70/0x98
[ 26.728710]
[ 26.728713] Freed by task 553:
[ 26.728716] kasan_save_stack+0x40/0x68
[ 26.728721] kasan_set_track+0x36/0x48
[ 26.728726] kasan_save_free_info+0x42/0x60
[ 26.728733] ____kasan_slab_free+0x17c/0x1e0
[ 26.728741] __kasan_slab_free+0x24/0x30
[ 26.728747] slab_free_freelist_hook+0x272/0x3a0
[ 26.728751] kmem_cache_free+0xec/0x540
[ 26.728757] event_trace_del_tracer+0x108/0x1f8
[ 26.728763] __remove_instance+0x242/0x668
[ 26.728781] instance_rmdir+0xc4/0x108
[ 26.728788] tracefs_syscall_rmdir+0xd4/0x160
[ 26.728796] vfs_rmdir+0x18a/0x538
[ 26.728802] do_rmdir+0x2c0/0x358
[ 26.728807] __s390x_sys_rmdir+0xd2/0x138
[ 26.728811] do_syscall+0x22c/0x328
[ 26.728817] __do_syscall+0x9a/0xf8
[ 26.728823] system_call+0x70/0x98
[ 26.728829]
[ 26.728833] The buggy address belongs to the object at 00000000107d3828
[ 26.728833] which belongs to the cache trace_event_file of size 96
[ 26.728841] The buggy address is located 16 bytes inside of
[ 26.728841] freed 96-byte region [00000000107d3828, 00000000107d3888)
[ 26.728846]
[ 26.728848] The buggy address belongs to the physical page:
[ 26.728851] page:000040000041f4c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x107d3
[ 26.728871] flags: 0x1ffff00000000200(slab|node=0|zone=0|lastcpupid=0x1ffff)
[ 26.728880] page_type: 0xffffffff()
[ 26.728889] raw: 1ffff00000000200 0000000005a2c100 0000400000891490 00004000006a89d0
[ 26.728894] raw: 0000000000000000 0013002600000000 ffffffff00000001 0000000000000000
[ 26.728898] page dumped because: kasan: bad access detected
[ 26.728902]
[ 26.728906] Memory state around the buggy address:
[ 26.728912] 00000000107d3700: fc fc fc fc fc fc fc fc fc fc fc fa fb fb fb fb
[ 26.728919] 00000000107d3780: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
[ 26.728928] >00000000107d3800: fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb
[ 26.728933] ^
[ 26.728940] 00000000107d3880: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fa
[ 26.728943] 00000000107d3900: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
[ 26.728946] ==================================================================
[ 26.728955] Disabling lock debugging due to kernel taint
[ 27.089717] Unable to handle kernel pointer dereference in virtual kernel address space
[ 27.089725] Failing address: 0d896d6d6d6d6000 TEID: 0d896d6d6d6d6803
[ 27.089729] Fault in home space mode while using kernel ASCE.
[ 27.089737] AS:00000000046b800b R2:0000000000000028
[ 27.089770] Oops: 0038 ilc:2 [#1] PREEMPT SMP
[ 27.089779] Modules linked in:
[ 27.089784] CPU: 1 PID: 514 Comm: ftracetest Tainted: G B 6.5.0-rc4-00014-g27152bceea1d #958
[ 27.089790] Hardware name: IBM 3931 A01 704 (z/VM 7.3.0)
[ 27.089794] Krnl PSW : 0404e00180000000 00000000005c4488 (trace_event_buffer_reserve+0xf0/0x3e8)
[ 27.089804] 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
[ 27.089810] Krnl GPRS: 0000000000000001 0000000000000001 6b6b6b6b6b6b6c5b 001c000000000000
[ 27.089816] 0d896d6d6d6d6d8b 00000000005c4702 001bff80013cf170 6b6b6b6b6b6b6b6b
[ 27.089822] 6b6b6b6b6b6b6b6b 00037ff000279e26 00000000107d3828 001bff80013cf208
[ 27.089827] 00000000031669f8 00000000026c1c1c 00000000005c4702 001bff80013cf078
[ 27.089843] Krnl Code: 00000000005c447a: 412080f0 la %r2,240(%r8)
[ 27.089843] 00000000005c447e: eb420003000c srlg %r4,%r2,3
[ 27.089843] #00000000005c4484: b9080043 agr %r4,%r3
[ 27.089843] >00000000005c4488: 95004000 cli 0(%r4),0
[ 27.089843] 00000000005c448c: a7740142 brc 7,00000000005c4710
[ 27.089843] 00000000005c4490: e3e080f00004 lg %r14,240(%r8)
[ 27.089843] 00000000005c4496: e3e0f0a80024 stg %r14,168(%r15)
[ 27.089843] 00000000005c449c: 412080f8 la %r2,248(%r8)
[ 27.089885] Call Trace:
[ 27.089890] [<00000000005c4488>] trace_event_buffer_reserve+0xf0/0x3e8
[ 27.089897] ([<00000000005c4702>] trace_event_buffer_reserve+0x36a/0x3e8)
[ 27.089903] [<000000000028979e>] trace_event_raw_event_sched_switch+0xce/0x430
[ 27.089910] [<00000000026a1cd4>] __schedule+0xba4/0x1f58
[ 27.089916] [<00000000026a4544>] preempt_schedule_irq+0xdc/0x190
[ 27.089925] [<000000000268f99c>] irqentry_exit+0xac/0x128
[ 27.089931] [<00000000026c1fac>] ext_int_handler+0xc4/0xf0
[ 27.089936] [<0000000000135a98>] __unwind_start+0x190/0x568
[ 27.089944] ([<0000000000135a7c>] __unwind_start+0x174/0x568)
[ 27.089950] [<000000000013bb90>] arch_stack_walk+0x130/0x1d0
[ 27.089957] [<0000000000424198>] stack_trace_save+0xc8/0xf8
[ 27.089968] [<00000000009d3468>] set_track_prepare+0x38/0x58
[ 27.089974] [<00000000009df35a>] free_to_partial_list+0x1ea/0x2f0
[ 27.089979] [<00000000009df656>] __slab_free+0x1f6/0x3c0
[ 27.089984] [<00000000009e19e8>] ___cache_free+0x158/0x188
[ 27.089989] [<00000000009e6df6>] qlist_free_all+0x7e/0x150
[ 27.089994] [<00000000009e752a>] kasan_quarantine_reduce+0x17a/0x1d8
[ 27.089999] [<00000000009e3488>] __kasan_slab_alloc+0x98/0xb8
[ 27.090005] [<00000000009de3fc>] kmem_cache_alloc+0x1ec/0x568
[ 27.090011] [<0000000000ab1d8e>] getname_flags.part.0+0x56/0x420
[ 27.090018] [<0000000000a81244>] do_sys_openat2+0xc4/0x178
00: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 00.
00: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 01.
[ 27.090027] [<0000000000a815ae>] do_sys_open+0xce/0x118
[ 27.090033] [<000000000010c5fc>] do_syscall+0x22c/0x328
[ 27.090040] [<000000000268e8b2>] __do_syscall+0x9a/0xf8
[ 27.090048] [<00000000026c1d28>] system_call+0x70/0x98
[ 27.090056] INFO: lockdep is turned off.
[ 27.090060] Last Breaking-Event-Address:
[ 27.090066] [<00000000005c4702>] trace_event_buffer_reserve+0x36a/0x3e8
[ 27.090077] Kernel panic - not syncing: Fatal exception: panic_on_oops