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ftrace: Have set_graph_functions handle write with RDWR 

Since reading the set_graph_functions uses seq functions, which sets the
file->private_data pointer to a seq_file descriptor. On writes the
ftrace_graph_data descriptor is set to file->private_data. But if the file
is opened for RDWR, the ftrace_graph_write() will incorrectly use the
file->private_data descriptor instead of
((struct seq_file *)file->private_data)->private pointer, and this can crash
the kernel.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2017-02-02 16:59:06 -05:00
parent d4ad9a1cca
commit ae98d27afc
1 changed files with 6 additions and 0 deletions
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6
kernel/trace/ftrace.c
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@ -4842,6 +4842,12 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX))
return -ENOMEM;
/* Read mode uses seq functions */
if (file->f_mode & FMODE_READ) {
struct seq_file *m = file->private_data;
fgd = m->private;
}
read = trace_get_user(&parser, ubuf, cnt, ppos);
if (read >= 0 && trace_parser_loaded((&parser))) {