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tracing: Fix tp_printk command line and trace events

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Masami added a wrapper to be able to unhash trace event pointers
 as they are only read by root anyway, and they can also be extracted
 by the raw trace data buffers. But this wrapper utilized the iterator
 to have a temporary buffer to manipulate the text with.
 
 tp_printk is a kernel command line option that will send the trace
 output of a trace event to the console on boot up (useful when the
 system crashes before finishing the boot). But the code used the same
 wrapper that Masami added, and its iterator did not have a buffer,
 and this caused the system to crash.
 
 Have the wrapper just print the trace event normally if the iterator
 has no temporary buffer.
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Merge tag 'trace-v5.12-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fix from Steven Rostedt:
 "Fix tp_printk command line and trace events

  Masami added a wrapper to be able to unhash trace event pointers as
  they are only read by root anyway, and they can also be extracted by
  the raw trace data buffers. But this wrapper utilized the iterator to
  have a temporary buffer to manipulate the text with.

  tp_printk is a kernel command line option that will send the trace
  output of a trace event to the console on boot up (useful when the
  system crashes before finishing the boot). But the code used the same
  wrapper that Masami added, and its iterator did not have a buffer, and
  this caused the system to crash.

  Have the wrapper just print the trace event normally if the iterator
  has no temporary buffer"

* tag 'trace-v5.12-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix checking event hash pointer logic when tp_printk is enabled
This commit is contained in:
Linus Torvalds 2021-04-20 14:38:35 -07:00
parent db2e718a47 0e1e71d349
commit 1fe5501ba1
1 changed files with 7 additions and 3 deletions
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10
kernel/trace/trace.c
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@ -3545,7 +3545,11 @@ static char *trace_iter_expand_format(struct trace_iterator *iter)
{
char *tmp;
if (iter->fmt == static_fmt_buf)
/*
* iter->tr is NULL when used with tp_printk, which makes
* this get called where it is not safe to call krealloc().
*/
if (!iter->tr || iter->fmt == static_fmt_buf)
return NULL;
tmp = krealloc(iter->fmt, iter->fmt_size + STATIC_FMT_BUF_SIZE,
@ -3566,7 +3570,7 @@ const char *trace_event_format(struct trace_iterator *iter, const char *fmt)
if (WARN_ON_ONCE(!fmt))
return fmt;
if (iter->tr->trace_flags & TRACE_ITER_HASH_PTR)
if (!iter->tr || iter->tr->trace_flags & TRACE_ITER_HASH_PTR)
return fmt;
p = fmt;
@ -9692,7 +9696,7 @@ void __init early_trace_init(void)
{
if (tracepoint_printk) {
tracepoint_print_iter =
kmalloc(sizeof(*tracepoint_print_iter), GFP_KERNEL);
kzalloc(sizeof(*tracepoint_print_iter), GFP_KERNEL);
if (MEM_FAIL(!tracepoint_print_iter,
"Failed to allocate trace iterator\n"))
tracepoint_printk = 0;