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Eiichi Tsukata 95067cbe54 tracing/snapshot: Resize spare buffer if size changed 
commit 46cc0b44428d0f0e81f11ea98217fc0edfbeab07 upstream.

Current snapshot implementation swaps two ring_buffers even though their
sizes are different from each other, that can cause an inconsistency
between the contents of buffer_size_kb file and the current buffer size.

For example:

  # cat buffer_size_kb
  7 (expanded: 1408)
  # echo 1 > events/enable
  # grep bytes per_cpu/cpu0/stats
  bytes: 1441020
  # echo 1 > snapshot             // current:1408, spare:1408
  # echo 123 > buffer_size_kb     // current:123,  spare:1408
  # echo 1 > snapshot             // current:1408, spare:123
  # grep bytes per_cpu/cpu0/stats
  bytes: 1443700
  # cat buffer_size_kb
  123                             // != current:1408

And also, a similar per-cpu case hits the following WARNING:

Reproducer:

  # echo 1 > per_cpu/cpu0/snapshot
  # echo 123 > buffer_size_kb
  # echo 1 > per_cpu/cpu0/snapshot

WARNING:

  WARNING: CPU: 0 PID: 1946 at kernel/trace/trace.c:1607 update_max_tr_single.part.0+0x2b8/0x380
  Modules linked in:
  CPU: 0 PID: 1946 Comm: bash Not tainted 5.2.0-rc6 #20
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-2.fc30 04/01/2014
  RIP: 0010:update_max_tr_single.part.0+0x2b8/0x380
  Code: ff e8 dc da f9 ff 0f 0b e9 88 fe ff ff e8 d0 da f9 ff 44 89 ee bf f5 ff ff ff e8 33 dc f9 ff 41 83 fd f5 74 96 e8 b8 da f9 ff <0f> 0b eb 8d e8 af da f9 ff 0f 0b e9 bf fd ff ff e8 a3 da f9 ff 48
  RSP: 0018:ffff888063e4fca0 EFLAGS: 00010093
  RAX: ffff888066214380 RBX: ffffffff99850fe0 RCX: ffffffff964298a8
  RDX: 0000000000000000 RSI: 00000000fffffff5 RDI: 0000000000000005
  RBP: 1ffff1100c7c9f96 R08: ffff888066214380 R09: ffffed100c7c9f9b
  R10: ffffed100c7c9f9a R11: 0000000000000003 R12: 0000000000000000
  R13: 00000000ffffffea R14: ffff888066214380 R15: ffffffff99851060
  FS:  00007f9f8173c700(0000) GS:ffff88806d000000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000714dc0 CR3: 0000000066fa6000 CR4: 00000000000006f0
  Call Trace:
   ? trace_array_printk_buf+0x140/0x140
   ? __mutex_lock_slowpath+0x10/0x10
   tracing_snapshot_write+0x4c8/0x7f0
   ? trace_printk_init_buffers+0x60/0x60
   ? selinux_file_permission+0x3b/0x540
   ? tracer_preempt_off+0x38/0x506
   ? trace_printk_init_buffers+0x60/0x60
   __vfs_write+0x81/0x100
   vfs_write+0x1e1/0x560
   ksys_write+0x126/0x250
   ? __ia32_sys_read+0xb0/0xb0
   ? do_syscall_64+0x1f/0x390
   do_syscall_64+0xc1/0x390
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

This patch adds resize_buffer_duplicate_size() to check if there is a
difference between current/spare buffer sizes and resize a spare buffer
if necessary.

Link: http://lkml.kernel.org/r/20190625012910.13109-1-devel@etsukata.com

Cc: stable@vger.kernel.org
Fixes: ad909e21bb ("tracing: Add internal tracing_snapshot() functions")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-08-04 09:34:50 +02:00
..
blktrace.c tracing/blktrace: Fix to allow setting same value 2018-09-09 20:04:34 +02:00
bpf_trace.c bpf: fix check of allowed specifiers in bpf_trace_printk 2018-12-17 21:55:10 +01:00
ftrace.c kprobes: Mark ftrace mcount handler functions nokprobe 2019-04-27 09:34:02 +02:00
Kconfig Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-11-10 18:11:41 -08:00
Makefile Makefile: Mute warning for __builtin_return_address(>0) for tracing only 2016-09-30 10:18:35 +02:00
power-traces.c
ring_buffer.c trace: Fix preempt_enable_no_resched() abuse 2019-05-16 19:44:43 +02:00
ring_buffer_benchmark.c ring_buffer: Remove unneeded smp_wmb() before wakeup of reader benchmark 2015-11-03 16:19:02 -05:00
rpm-traces.c
trace.c tracing/snapshot: Resize spare buffer if size changed 2019-08-04 09:34:50 +02:00
trace.h tracing: Silence GCC 9 array bounds warning 2019-07-10 09:56:31 +02:00
trace_benchmark.c tracing: Only benchmark the time tracepoints take if tracing is on 2015-11-02 13:34:58 -05:00
trace_benchmark.h
trace_branch.c tracing: Remove {start,stop}_branch_trace 2015-10-21 10:10:09 -04:00
trace_clock.c
trace_entries.h
trace_event_perf.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
trace_events.c tracing: Fix partial reading of trace event's id file 2019-06-11 12:23:46 +02:00
trace_events_filter.c tracing: Fix regex_match_front() to not over compare the test string 2018-05-16 10:06:51 +02:00
trace_events_filter_test.h
trace_events_trigger.c tracing: Fix memory leak in set_trigger_filter() 2018-12-21 14:09:51 +01:00
trace_export.c tracing: ftrace_event_is_function() can return boolean 2015-11-02 14:28:05 -05:00
trace_functions.c
trace_functions_graph.c tracing: Fix missing return symbol in function_graph output 2018-07-11 16:03:48 +02:00
trace_irqsoff.c tracing: Have preempt(irqs)off trace preempt disabled functions 2016-04-12 09:08:59 -07:00
trace_kdb.c tracing: Silence GCC 9 array bounds warning 2019-07-10 09:56:31 +02:00
trace_kprobe.c tracing: Quiet gcc warning about maybe unused link variable 2018-08-06 16:24:30 +02:00
trace_mmiotrace.c tracing: Pass trace_array into trace_buffer_unlock_commit() 2015-09-25 17:38:44 -04:00
trace_nop.c
trace_output.c tracing: Move trace_flags from global to a trace_array field 2015-09-30 15:22:55 -04:00
trace_output.h tracing: Turn seq_print_user_ip() into a static function 2015-09-28 10:16:12 -04:00
trace_printk.c tracing: Handle NULL formats in hold_module_trace_bprintk_format() 2016-07-27 09:47:32 -07:00
trace_probe.c tracing: probeevent: Fix to support minus offset from symbol 2018-03-28 18:40:15 +02:00
trace_probe.h tracing: probeevent: Fix to support minus offset from symbol 2018-03-28 18:40:15 +02:00
trace_sched_switch.c sched/core: Fix trace_sched_switch() 2015-10-06 17:08:15 +02:00
trace_sched_wakeup.c Most of the changes are clean ups and small fixes. Some of them have 2015-11-06 13:30:20 -08:00
trace_selftest.c ftrace: Fix selftest goto location on error 2017-09-27 11:00:16 +02:00
trace_selftest_dynamic.c
trace_seq.c
trace_stack.c tracing/stacktrace: Show entire trace if passed in function not found 2016-02-17 12:30:57 -08:00
trace_stat.c
trace_stat.h
trace_syscalls.c tracing: Move trace_flags from global to a trace_array field 2015-09-30 15:22:55 -04:00
trace_uprobe.c tracing/uprobes: Fix output for multiple string arguments 2019-02-20 10:13:22 +01:00