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Steven Rostedt (VMware) 2d349b0a69 tracing / histogram: Fix NULL pointer dereference on strcmp() on NULL event name 
[ Upstream commit 5acce0bff2a0420ce87d4591daeb867f47d552c2 ]

The following commands:

 # echo 'read_max u64 size;' > synthetic_events
 # echo 'hist:keys=common_pid:count=count:onmax($count).trace(read_max,count)' > events/syscalls/sys_enter_read/trigger

Causes:

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: 0000 [#1] PREEMPT SMP
 CPU: 4 PID: 1763 Comm: bash Not tainted 5.14.0-rc2-test+ #155
 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01
v03.03 07/14/2016
 RIP: 0010:strcmp+0xc/0x20
 Code: 75 f7 31 c0 0f b6 0c 06 88 0c 02 48 83 c0 01 84 c9 75 f1 4c 89 c0
c3 0f 1f 80 00 00 00 00 31 c0 eb 08 48 83 c0 01 84 d2 74 0f <0f> b6 14 07
3a 14 06 74 ef 19 c0 83 c8 01 c3 31 c0 c3 66 90 48 89
 RSP: 0018:ffffb5fdc0963ca8 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: ffffffffb3a4e040 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: ffff9714c0d0b640 RDI: 0000000000000000
 RBP: 0000000000000000 R08: 00000022986b7cde R09: ffffffffb3a4dff8
 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9714c50603c8
 R13: 0000000000000000 R14: ffff97143fdf9e48 R15: ffff9714c01a2210
 FS:  00007f1fa6785740(0000) GS:ffff9714da400000(0000)
knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 000000002d863004 CR4: 00000000001706e0
 Call Trace:
  __find_event_file+0x4e/0x80
  action_create+0x6b7/0xeb0
  ? kstrdup+0x44/0x60
  event_hist_trigger_func+0x1a07/0x2130
  trigger_process_regex+0xbd/0x110
  event_trigger_write+0x71/0xd0
  vfs_write+0xe9/0x310
  ksys_write+0x68/0xe0
  do_syscall_64+0x3b/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae
 RIP: 0033:0x7f1fa6879e87

The problem was the "trace(read_max,count)" where the "count" should be
"$count" as "onmax()" only handles variables (although it really should be
able to figure out that "count" is a field of sys_enter_read). But there's
a path that does not find the variable and ends up passing a NULL for the
event, which ends up getting passed to "strcmp()".

Add a check for NULL to return and error on the command with:

 # cat error_log
  hist:syscalls:sys_enter_read: error: Couldn't create or find variable
  Command: hist:keys=common_pid:count=count:onmax($count).trace(read_max,count)
                                ^
Link: https://lkml.kernel.org/r/20210808003011.4037f8d0@oasis.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 50450603ec tracing: Add 'onmax' hist trigger action support
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-08-26 08:36:47 -04:00
..
blktrace.c blktrace: fix debugfs use after free 2020-11-10 12:35:54 +01:00
bpf_trace.c tracepoint: Add tracepoint_probe_register_may_exist() for BPF tracing 2021-07-20 16:15:42 +02:00
ftrace.c ftrace: Do not blindly read the ip address in ftrace_bug() 2021-06-16 11:55:02 +02:00
Kconfig tracing/kprobes: Do the notrace functions check without kprobes on ftrace 2021-01-19 18:22:35 +01:00
Makefile tracing: Allow gcov profiling on only ftrace subsystem 2018-08-21 09:11:49 -04:00
power-traces.c
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 tracing: Fix bug in rb_per_cpu_empty() that might cause deadloop. 2021-07-28 11:13:50 +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
trace.c tracing/histogram: Rename "cpu" to "common_cpu" 2021-08-12 13:19:42 +02:00
trace.h tracing: Fix userstacktrace option for instances 2020-12-11 13:25:03 +01:00
trace_benchmark.c
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: Do no increment trace_clock_global() by one 2021-06-30 08:48:23 -04:00
trace_entries.h tracing: Set kernel_stack's caller size properly 2020-10-01 13:14:31 +02:00
trace_event_perf.c tracing: Fix race in perf_trace_buf initialization 2019-10-29 09:20:03 +01:00
trace_events.c tracing: Do not count ftrace events in top level enable output 2021-02-23 15:00:55 +01:00
trace_events_filter.c tracing: Have error path in predicate_parse() free its allocated memory 2020-08-05 10:05:59 +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 / histogram: Fix NULL pointer dereference on strcmp() on NULL event name 2021-08-26 08:36:47 -04:00
trace_events_trigger.c tracing: Fix event trigger to accept redundant spaces 2020-06-30 23:17:17 -04:00
trace_export.c
trace_functions.c
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: Remove WARN_ON in start_thread() 2020-12-08 10:18:55 +01:00
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/kprobe: Fix to support kretprobe events on unloaded modules 2021-02-13 13:51:13 +01:00
trace_kprobe_selftest.c
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
trace_nop.c
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 lockdep: fix order in trace_hardirqs_off_caller() 2020-10-01 13:14:50 +02:00
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 tracing: Fix sched switch start/stop refcount racy updates 2020-02-11 04:33:55 -08:00
trace_sched_wakeup.c kernel/trace: Fix do not unregister tracepoints when register sched_migrate_task fail 2020-01-14 20:06:59 +01:00
trace_selftest.c ftrace: Handle tracing when switching between context 2020-11-10 12:35:58 +01:00
trace_selftest_dynamic.c
trace_seq.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_stack.c tracing: Have stack tracer compile when MCOUNT_INSN_SIZE is not defined 2020-01-14 20:06:59 +01:00
trace_stat.c tracing: Fix very unlikely race of registering two stat tracers 2020-02-24 08:34:39 +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
trace_uprobe.c tracing/uprobes: Fix output for multiple string arguments 2019-02-20 10:25:48 +01:00
tracing_map.c tracing: Have the histogram compare functions convert to u64 first 2020-01-09 10:19:02 +01:00
tracing_map.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00