Messages in this thread | | | Date | Mon, 15 Jan 2018 18:20:00 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH v2 1/3] tracing: detect the string termination character when parsing user input string |
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On Mon, 15 Jan 2018 19:41:12 +0800 changbin.du@intel.com wrote:
> From: Changbin Du <changbin.du@intel.com> > > The usersapce can give a '\0' terminated C string in the input buffer. > Before this change, trace_get_user() will return a parsed string "\0" in > below case which is not expected (expects it skip all inputs) and cause the > caller failed.
The above totally does not parse (no pun intended).
Are you trying to say:
"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 > > This patch try to make the parser '\0' aware to fix such issue. When parser > sees a '\0' it stops further parsing. With this change, write(3, " \0", 2) > will work.
The above should be something like:
"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."
-- Steve
> > Signed-off-by: Changbin Du <changbin.du@intel.com> > > --- > v2: Stop parsing when '\0' found. > --- > kernel/trace/trace.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 2a8d8a2..144d08e 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1237,7 +1237,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* only spaces were written */ > - if (isspace(ch)) { > + if (isspace(ch) || !ch) { > *ppos += read; > ret = read; > goto out; > @@ -1247,7 +1247,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* read the non-space input */ > - while (cnt && !isspace(ch)) { > + while (cnt && !isspace(ch) && ch) { > if (parser->idx < parser->size - 1) > parser->buffer[parser->idx++] = ch; > else { > @@ -1262,7 +1262,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* We either got finished input or we have to wait for another call. */ > - if (isspace(ch)) { > + if (isspace(ch) || !ch) { > parser->buffer[parser->idx] = 0; > parser->cont = false; > } else if (parser->idx < parser->size - 1) {
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