[for-linus][PATCH] ftrace: Handle commands when closing set_ftrace_filter file

[for-linus][PATCH] ftrace: Handle commands when closing set_ftrace_filter file

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
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Head SHA1: 8c9af478c06bb1ab1422f90d8ecbc53defd44bc3


Steven Rostedt (VMware) (1):
      ftrace: Handle commands when closing set_ftrace_filter file

----
 kernel/trace/ftrace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---------------------------
commit 8c9af478c06bb1ab1422f90d8ecbc53defd44bc3
Author: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date:   Wed May 5 10:38:24 2021 -0400

    ftrace: Handle commands when closing set_ftrace_filter file
    
     # echo switch_mm:traceoff > /sys/kernel/tracing/set_ftrace_filter
    
    will cause switch_mm to stop tracing by the traceoff command.
    
     # echo -n switch_mm:traceoff > /sys/kernel/tracing/set_ftrace_filter
    
    does nothing.
    
    The reason is that the parsing in the write function only processes
    commands if it finished parsing (there is white space written after the
    command). That's to handle:
    
     write(fd, "switch_mm:", 10);
     write(fd, "traceoff", 8);
    
    cases, where the command is broken over multiple writes.
    
    The problem is if the file descriptor is closed, then the write call is
    not processed, and the command needs to be processed in the release code.
    The release code can handle matching of functions, but does not handle
    commands.
    
    Cc: stable@vger.kernel.org
    Fixes: eda1e32855656 ("tracing: handle broken names in ftrace filter")
    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 057e962ca5ce..c57508445faa 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5591,7 +5591,10 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
 	parser = &iter->parser;
 	if (trace_parser_loaded(parser)) {
-		ftrace_match_records(iter->hash, parser->buffer, parser->idx);
+		int enable = !(iter->flags & FTRACE_ITER_NOTRACE);
+
+		ftrace_process_regex(iter, parser->buffer,
+				     parser->idx, enable);
 	}
 
 	trace_parser_put(parser);