[PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[changbin.du]

From: Changbin Du <changbin.du@intel.com>

I found there are some problems in the tracing parser when I investiage the root
cause of issues mentioned in below patch.
https://patchwork.kernel.org/patch/10132953/

This serials can fix them.

v3: Polish commit msg from Steven Rostedt.
v2:
  - Drop 1 old patch and add a new one.
  - Stop parsing when '\0' found.

Changbin Du (3):
  tracing: detect the string termination character when parsing user
    input string
  tracing: clear parser->idx if parser gets nothing
  tracing: make sure the parsed string always terminates with '\0'

 kernel/trace/ftrace.c       |  2 --
 kernel/trace/trace.c        | 14 +++++++-------
 kernel/trace/trace_events.c |  2 --
 3 files changed, 7 insertions(+), 11 deletions(-)

-- 
2.7.4

[PATCH v3 1/3] tracing: detect the string termination character when parsing user input string

[changbin.du]

From: Changbin Du <changbin.du@intel.com>

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.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Changbin Du <changbin.du@intel.com>

---
  v3: Polish commit msg from Steven Rostedt.
  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) {
-- 
2.7.4

[PATCH v3 2/3] tracing: clear parser->idx if parser gets nothing

[changbin.du]

From: Changbin Du <changbin.du@intel.com>

If only spaces was got in that cycle, we should clear parser->idx to make
trace_parser_loaded() return false.

Signed-off-by: Changbin Du <changbin.du@intel.com>
---
 kernel/trace/trace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 144d08e..b44926e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1236,14 +1236,14 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 			cnt--;
 		}
 
+		parser->idx = 0;
+
 		/* only spaces were written */
 		if (isspace(ch) || !ch) {
 			*ppos += read;
 			ret = read;
 			goto out;
 		}
-
-		parser->idx = 0;
 	}
 
 	/* read the non-space input */
-- 
2.7.4

[PATCH v3 3/3] tracing: make sure the parsed string always terminates with '\0'

[changbin.du]

From: Changbin Du <changbin.du@intel.com>

Always mark the parsed string with a terminated '\0' even parser expects
another input to be parsed. Thus the users needn't append '0' before
using parsed string if new input is not given.

Signed-off-by: Changbin Du <changbin.du@intel.com>
---
 kernel/trace/ftrace.c       | 2 --
 kernel/trace/trace.c        | 4 ++--
 kernel/trace/trace_events.c | 2 --
 3 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ccdf366..3addb82 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5010,7 +5010,6 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
 	parser = &iter->parser;
 	if (trace_parser_loaded(parser)) {
-		parser->buffer[parser->idx] = 0;
 		ftrace_match_records(iter->hash, parser->buffer, parser->idx);
 	}
 
@@ -5324,7 +5323,6 @@ ftrace_graph_release(struct inode *inode, struct file *file)
 		parser = &fgd->parser;
 
 		if (trace_parser_loaded((parser))) {
-			parser->buffer[parser->idx] = 0;
 			ret = ftrace_graph_set_hash(fgd->new_hash,
 						    parser->buffer);
 		}
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b44926e..8f7fea2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -530,8 +530,6 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
 		ubuf += ret;
 		cnt -= ret;
 
-		parser.buffer[parser.idx] = 0;
-
 		ret = -EINVAL;
 		if (kstrtoul(parser.buffer, 0, &val))
 			break;
@@ -1268,6 +1266,8 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 	} else if (parser->idx < parser->size - 1) {
 		parser->cont = true;
 		parser->buffer[parser->idx++] = ch;
+		/* Make sure the parsed string always terminates with '\0'. */
+		parser->buffer[parser->idx] = 0;
 	} else {
 		ret = -EINVAL;
 		goto out;
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index ec0f9aa..7f8027c 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -885,8 +885,6 @@ ftrace_event_write(struct file *file, const char __user *ubuf,
 		if (*parser.buffer == '!')
 			set = 0;
 
-		parser.buffer[parser.idx] = 0;
-
 		ret = ftrace_set_clr_event(tr, parser.buffer + !set, set);
 		if (ret)
 			goto out_put;
-- 
2.7.4

Re: [PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[Steven Rostedt]

On Tue, 16 Jan 2018 17:02:27 +0800
changbin.du@intel.com wrote:

> From: Changbin Du <changbin.du@intel.com>
> 
> I found there are some problems in the tracing parser when I investiage the root
> cause of issues mentioned in below patch.
> https://patchwork.kernel.org/patch/10132953/

I pulled in your patches and tweaked the change logs of the other two
patches as well. You can see my temporary git tree here, but it may
rebase.

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git

 ftrace/core

-- Steve

Re: [PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[Du, Changbin]

On Tue, Jan 16, 2018 at 12:42:26PM -0500, Steven Rostedt wrote:
> On Tue, 16 Jan 2018 17:02:27 +0800
> changbin.du@intel.com wrote:
> 
> > From: Changbin Du <changbin.du@intel.com>
> > 
> > I found there are some problems in the tracing parser when I investiage the root
> > cause of issues mentioned in below patch.
> > https://patchwork.kernel.org/patch/10132953/
> 
> I pulled in your patches and tweaked the change logs of the other two
> patches as well. You can see my temporary git tree here, but it may
> rebase.
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> 
>  ftrace/core
> 
> -- Steve
Got it. Thank you!

Hi Olsa, so the perf patch 'perf ftrace: Fix the buffer size in__write_tracing_file'
is still needed. I will resend you at appropriate time.

-- 
Thanks,
Changbin Du

Re: [PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[Namhyung Kim]

Hello,

On Wed, Jan 17, 2018 at 12:54:34PM +0800, Du, Changbin wrote:
> On Tue, Jan 16, 2018 at 12:42:26PM -0500, Steven Rostedt wrote:
> > On Tue, 16 Jan 2018 17:02:27 +0800
> > changbin.du@intel.com wrote:
> > 
> > > From: Changbin Du <changbin.du@intel.com>
> > > 
> > > I found there are some problems in the tracing parser when I investiage the root
> > > cause of issues mentioned in below patch.
> > > https://patchwork.kernel.org/patch/10132953/
> > 
> > I pulled in your patches and tweaked the change logs of the other two
> > patches as well. You can see my temporary git tree here, but it may
> > rebase.
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> > 
> >  ftrace/core
> > 
> > -- Steve
> Got it. Thank you!
> 
> Hi Olsa, so the perf patch 'perf ftrace: Fix the buffer size in__write_tracing_file'
> is still needed. I will resend you at appropriate time.

But it will work on the future kernels only, right?  For tools to be
compatible with old kernels, you'd better writing a whitespace after
the function name IMHO.

Thanks,
Namhyung

Re: [PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[Du, Changbin]

On Wed, Jan 17, 2018 at 02:45:24PM +0900, Namhyung Kim wrote:
> Hello,
> 
> On Wed, Jan 17, 2018 at 12:54:34PM +0800, Du, Changbin wrote:
> > On Tue, Jan 16, 2018 at 12:42:26PM -0500, Steven Rostedt wrote:
> > > On Tue, 16 Jan 2018 17:02:27 +0800
> > > changbin.du@intel.com wrote:
> > > 
> > > > From: Changbin Du <changbin.du@intel.com>
> > > > 
> > > > I found there are some problems in the tracing parser when I investiage the root
> > > > cause of issues mentioned in below patch.
> > > > https://patchwork.kernel.org/patch/10132953/
> > > 
> > > I pulled in your patches and tweaked the change logs of the other two
> > > patches as well. You can see my temporary git tree here, but it may
> > > rebase.
> > > 
> > > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> > > 
> > >  ftrace/core
> > > 
> > > -- Steve
> > Got it. Thank you!
> > 
> > Hi Olsa, so the perf patch 'perf ftrace: Fix the buffer size in__write_tracing_file'
> > is still needed. I will resend you at appropriate time.
> 
> But it will work on the future kernels only, right?  For tools to be
> compatible with old kernels, you'd better writing a whitespace after
> the function name IMHO.
> 
Yes, it needs to write a space if it doesn't want possible error hidden.

> Thanks,
> Namhyung

-- 
Thanks,
Changbin Du

Re: [PATCH v3 0/3] tracing: Fix the parser when processing strings w/ or w/o terminated '\0'

[Namhyung Kim]

On Tue, Jan 16, 2018 at 05:02:27PM +0800, changbin.du@intel.com wrote:
> From: Changbin Du <changbin.du@intel.com>
> 
> I found there are some problems in the tracing parser when I investiage the root
> cause of issues mentioned in below patch.
> https://patchwork.kernel.org/patch/10132953/
> 
> This serials can fix them.
> 
> v3: Polish commit msg from Steven Rostedt.
> v2:
>   - Drop 1 old patch and add a new one.
>   - Stop parsing when '\0' found.
> 
> Changbin Du (3):
>   tracing: detect the string termination character when parsing user
>     input string
>   tracing: clear parser->idx if parser gets nothing
>   tracing: make sure the parsed string always terminates with '\0'

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung


> 
>  kernel/trace/ftrace.c       |  2 --
>  kernel/trace/trace.c        | 14 +++++++-------
>  kernel/trace/trace_events.c |  2 --
>  3 files changed, 7 insertions(+), 11 deletions(-)
> 
> -- 
> 2.7.4
> 
> --
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