Messages in this thread | | | Date | Tue, 9 Jan 2018 17:54:34 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 1/3] tracing: detect the string termination character when parsing user input string |
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On Tue, 9 Jan 2018 17:55:46 +0800 changbin.du@intel.com wrote:
> From: Changbin Du <changbin.du@intel.com> > > The usersapce can give a '\0' terminated C string or even has '\0' at the > middle of input buffer. We need handle both these two cases correctly.
What do you define as correctly. Because I'm not seeing it.
> > Before this change, trace_get_user() will return a parsed string "\0" in > below case. It is not expected (expects it skip all inputs) and cause the > caller failed. > > open("/sys/kernel/debug/tracing//set_ftrace_pid", O_WRONLY|O_TRUNC) = 3 > write(3, " \0", 2) = -1 EINVAL (Invalid argument)
That looks more like a feature and not a bug.
> > This patch try to make the parser '\0' aware to fix such issue.
Why?
> > Since the caller expects trace_get_user() to parse whole input buffer, so > this patch treat '\0' as a separator as whitespace.
It looks more like we are trying to fix a userspace bug via the kernel.
I'm not liking this. So NACK.
-- Steve
> > Signed-off-by: Changbin Du <changbin.du@intel.com> > --- > kernel/trace/trace.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 2a8d8a2..18526a1 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1194,9 +1194,14 @@ void trace_parser_put(struct trace_parser *parser) > parser->buffer = NULL; > } > > +static inline bool is_space_or_zero(char ch) > +{ > + return isspace(ch) || !ch; > +} > + > /* > - * trace_get_user - reads the user input string separated by space > - * (matched by isspace(ch)) > + * trace_get_user - reads the user input string separated by space or '\0' > + * (matched by is_space_or_zero(ch)) > * > * For each string found the 'struct trace_parser' is updated, > * and the function returns. > @@ -1228,7 +1233,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > */ > if (!parser->cont) { > /* skip white space */ > - while (cnt && isspace(ch)) { > + while (cnt && is_space_or_zero(ch)) { > ret = get_user(ch, ubuf++); > if (ret) > goto out; > @@ -1237,7 +1242,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* only spaces were written */ > - if (isspace(ch)) { > + if (is_space_or_zero(ch)) { > *ppos += read; > ret = read; > goto out; > @@ -1247,7 +1252,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* read the non-space input */ > - while (cnt && !isspace(ch)) { > + while (cnt && !is_space_or_zero(ch)) { > if (parser->idx < parser->size - 1) > parser->buffer[parser->idx++] = ch; > else { > @@ -1262,7 +1267,7 @@ 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 (is_space_or_zero(ch)) { > parser->buffer[parser->idx] = 0; > parser->cont = false; > } else if (parser->idx < parser->size - 1) {
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