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Prateek Sood 5ce7528c4d tracing: Fix race in perf_trace_buf initialization 
commit 6b1340cc00 upstream.

A race condition exists while initialiazing perf_trace_buf from
perf_trace_init() and perf_kprobe_init().

      CPU0                                        CPU1
perf_trace_init()
  mutex_lock(&event_mutex)
    perf_trace_event_init()
      perf_trace_event_reg()
        total_ref_count == 0
	buf = alloc_percpu()
        perf_trace_buf[i] = buf
        tp_event->class->reg() //fails       perf_kprobe_init()
	goto fail                              perf_trace_event_init()
                                                 perf_trace_event_reg()
        fail:
	  total_ref_count == 0

                                                   total_ref_count == 0
                                                   buf = alloc_percpu()
                                                   perf_trace_buf[i] = buf
                                                   tp_event->class->reg()
                                                   total_ref_count++

          free_percpu(perf_trace_buf[i])
          perf_trace_buf[i] = NULL

Any subsequent call to perf_trace_event_reg() will observe total_ref_count > 0,
causing the perf_trace_buf to be always NULL. This can result in perf_trace_buf
getting accessed from perf_trace_buf_alloc() without being initialized. Acquiring
event_mutex in perf_kprobe_init() before calling perf_trace_event_init() should
fix this race.

The race caused the following bug:

 Unable to handle kernel paging request at virtual address 0000003106f2003c
 Mem abort info:
   ESR = 0x96000045
   Exception class = DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
 Data abort info:
   ISV = 0, ISS = 0x00000045
   CM = 0, WnR = 1
 user pgtable: 4k pages, 39-bit VAs, pgdp = ffffffc034b9b000
 [0000003106f2003c] pgd=0000000000000000, pud=0000000000000000
 Internal error: Oops: 96000045 [#1] PREEMPT SMP
 Process syz-executor (pid: 18393, stack limit = 0xffffffc093190000)
 pstate: 80400005 (Nzcv daif +PAN -UAO)
 pc : __memset+0x20/0x1ac
 lr : memset+0x3c/0x50
 sp : ffffffc09319fc50

  __memset+0x20/0x1ac
  perf_trace_buf_alloc+0x140/0x1a0
  perf_trace_sys_enter+0x158/0x310
  syscall_trace_enter+0x348/0x7c0
  el0_svc_common+0x11c/0x368
  el0_svc_handler+0x12c/0x198
  el0_svc+0x8/0xc

Ramdumps showed the following:
  total_ref_count = 3
  perf_trace_buf = (
      0x0 -> NULL,
      0x0 -> NULL,
      0x0 -> NULL,
      0x0 -> NULL)

Link: http://lkml.kernel.org/r/1571120245-4186-1-git-send-email-prsood@codeaurora.org

Cc: stable@vger.kernel.org
Fixes: e12f03d703 ("perf/core: Implement the 'perf_kprobe' PMU")
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Prateek Sood <prsood@codeaurora.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-10-29 09:20:03 +01:00
..
blktrace.c for-4.19/post-20180822 2018-08-22 13:38:05 -07:00
bpf_trace.c bpf: fix nested bpf tracepoints with per-cpu data 2019-07-03 13:14:48 +02:00
ftrace.c ftrace: Get a reference counter for the trace_array on filter files 2019-10-17 13:45:40 -07:00
Kconfig Masami found an off by one bug in the code that keeps "notrace" functions 2018-08-23 13:07:00 -07:00
Makefile tracing: Allow gcov profiling on only ftrace subsystem 2018-08-21 09:11:49 -04:00
power-traces.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
preemptirq_delay_test.c tracing: Use trace_clock_local() for looping in preemptirq_delay_test.c 2018-10-17 15:35:33 -04:00
ring_buffer.c trace: Fix preempt_enable_no_resched() abuse 2019-05-02 09:58:54 +02:00
ring_buffer_benchmark.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
rpm-traces.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace.c tracing: Get trace_array reference for available_tracers files 2019-10-17 13:45:41 -07:00
trace.h tracing: Silence GCC 9 array bounds warning 2019-06-25 11:35:52 +08:00
trace_benchmark.c rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs() 2018-05-15 10:27:29 -07:00
trace_benchmark.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_branch.c Revert "x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP" 2019-07-03 13:14:41 +02:00
trace_clock.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_entries.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_event_perf.c tracing: Fix race in perf_trace_buf initialization 2019-10-29 09:20:03 +01:00
trace_events.c tracing: Fix partial reading of trace event's id file 2019-05-25 18:23:32 +02:00
trace_events_filter.c tracing: Avoid memory leak in predicate_parse() 2019-06-09 09:17:14 +02:00
trace_events_filter_test.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_events_hist.c tracing: Make sure variable reference alias has correct var_ref_idx 2019-10-11 18:20:57 +02:00
trace_events_trigger.c tracing: Fix memory leak in set_trigger_filter() 2018-12-19 19:19:52 +01:00
trace_export.c tracing: Add trigger file for trace_markers tracefs/ftrace/print 2018-05-29 08:28:53 -04:00
trace_functions.c tracing: Update stack trace skipping for ORC unwinder 2018-01-23 15:57:00 -05:00
trace_functions_graph.c tracing/fgraph: Fix set_graph_function from showing interrupts 2018-12-08 12:59:07 +01:00
trace_hwlat.c tracing/hwlat: Don't ignore outer-loop duration when calculating max_latency 2019-10-17 13:45:39 -07:00
trace_irqsoff.c tracing/fgraph: Fix set_graph_function from showing interrupts 2018-12-08 12:59:07 +01:00
trace_kdb.c tracing: Silence GCC 9 array bounds warning 2019-06-25 11:35:52 +08:00
trace_kprobe.c tracing/kprobes: Check the probe on unloaded module correctly 2018-11-21 09:19:09 +01:00
trace_kprobe_selftest.c selftest/ftrace: Move kprobe selftest function to separate compile unit 2018-07-30 18:41:04 -04:00
trace_kprobe_selftest.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_mmiotrace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_nop.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_output.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_output.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_preemptirq.c tracing: More reverting of "tracing: Centralize preemptirq tracepoints and unify their usage" 2018-08-10 15:12:00 -04:00
trace_printk.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_probe.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_probe.h tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_sched_switch.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_sched_wakeup.c tracing/fgraph: Fix set_graph_function from showing interrupts 2018-12-08 12:59:07 +01:00
trace_selftest.c Tracing updates for 4.15: 2017-11-17 14:58:01 -08:00
trace_selftest_dynamic.c ftrace: Mark function tracer test functions noinline/noclone 2018-01-23 15:57:29 -05:00
trace_seq.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_stack.c tracing: Fix the file mode of stack tracer 2018-05-03 11:58:05 -04:00
trace_stat.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_stat.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_syscalls.c Tracing updates for 4.15: 2017-11-17 14:58:01 -08:00
trace_uprobe.c tracing/uprobes: Fix output for multiple string arguments 2019-02-20 10:25:48 +01:00
tracing_map.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
tracing_map.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00