tracing: Detect the string nul character when parsing user input string
authorChangbin Du <changbin.du@intel.com>
Tue, 16 Jan 2018 09:02:28 +0000 (17:02 +0800)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Tue, 23 Jan 2018 20:57:27 +0000 (15:57 -0500)
commit921a7acd85ebbab1b3cd99828e6842fd3e78df24
tree3fa8375014270e69a605f50b86e5c9b4d07620bd
parent2ee5b92a2598d9e403337185fdf88f661dee8616
tracing: Detect the string nul character when parsing user input string

User space can pass in a C nul character '\0' along with its input. The
function trace_get_user() will try to process it as a normal character,
and that will fail to parse.

open("/sys/kernel/debug/tracing//set_ftrace_pid", O_WRONLY|O_TRUNC) = 3
write(3, " \0", 2)                      = -1 EINVAL (Invalid argument)

while parse can handle spaces, so below works.

$ echo "" > set_ftrace_pid
$ echo " " > set_ftrace_pid
$ echo -n " " > set_ftrace_pid

Have the parser stop on '\0' and cease any further parsing. Only process
the characters up to the nul '\0' character and do not process it.

Link: http://lkml.kernel.org/r/1516093350-12045-2-git-send-email-changbin.du@intel.com
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
kernel/trace/trace.c