[PATCH 0/2] Replace the use of simple_strtol/ul functions with kstrto

[PATCH 0/2] Replace the use of simple_strtol/ul functions with kstrto

[Yuran Pereira]

The simple_str* family of functions perform no error checking in
scenarios where the input value overflows the intended output variable.
This results in these function successfully returning even when the
output does not match the input string.

Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
simple_strtoul(), and simple_strtoull() functions explicitly ignore
overflows, which may lead to unexpected results in callers."
Hence, the use of those functions is discouraged.

This patch series replaces uses of the simple_strto* series of function
with the safer  kstrto* alternatives.

  
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull

Yuran Pereira (2):
  kdb: Replace the use of simple_strto with safer kstrto in kdb_main
  trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

 kernel/debug/kdb/kdb_main.c | 70 +++++++++++--------------------------
 kernel/trace/trace_kdb.c    | 14 ++++----
 2 files changed, 27 insertions(+), 57 deletions(-)

-- 
2.25.1

[PATCH 1/2] kdb: Replace the use of simple_strto with safer kstrto in kdb_main

[Yuran Pereira]

The simple_str* family of functions perform no error checking in
scenarios where the input value overflows the intended output variable.
This results in these functions successfully returning even when the
output does not match the input string.

Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
simple_strtoul(), and simple_strtoull() functions explicitly ignore
overflows, which may lead to unexpected results in callers."
Hence, the use of those functions is discouraged.

This patch replaces all uses of the simple_strto* series of functions
with their safer kstrto* alternatives.

Side effects of this patch:
- Every string to long or long long conversion using kstrto* is now
  checked for failure.
- kstrto* errors are handled with appropriate `KDB_BADINT` wherever
  applicable.
- A good side effect is that we end up saving a few lines of code
  since unlike in simple_strto* functions, kstrto functions do not
  need an additional "end pointer" variable, and the return values
  of the latter can be directly checked in an "if" statement without
  the need to define additional `ret` or `err` variables.
  This, of course, results in cleaner, yet still easy to understand
  code.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull

Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
---
 kernel/debug/kdb/kdb_main.c | 70 +++++++++++--------------------------
 1 file changed, 21 insertions(+), 49 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 6b213c8252d6..a6e4bec7854d 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -316,8 +316,8 @@ static int kdbgetulenv(const char *match, unsigned long *value)
 		return KDB_NOTENV;
 	if (strlen(ep) == 0)
 		return KDB_NOENVVALUE;
-
-	*value = simple_strtoul(ep, NULL, 0);
+	if (kstrtoul(ep, 0, value))
+		return KDB_BADINT;
 
 	return 0;
 }
@@ -412,42 +412,21 @@ static void kdb_printenv(void)
  */
 int kdbgetularg(const char *arg, unsigned long *value)
 {
-	char *endp;
-	unsigned long val;
-
-	val = simple_strtoul(arg, &endp, 0);
-
-	if (endp == arg) {
-		/*
-		 * Also try base 16, for us folks too lazy to type the
-		 * leading 0x...
-		 */
-		val = simple_strtoul(arg, &endp, 16);
-		if (endp == arg)
+	/*
+	 * If the first fails, also try base 16, for us
+	 * folks too lazy to type the leading 0x...
+	 */
+	if (kstrtoul(arg, 0, value))
+		if (kstrtoul(arg, 16, value))
 			return KDB_BADINT;
-	}
-
-	*value = val;
-
 	return 0;
 }
 
 int kdbgetu64arg(const char *arg, u64 *value)
 {
-	char *endp;
-	u64 val;
-
-	val = simple_strtoull(arg, &endp, 0);
-
-	if (endp == arg) {
-
-		val = simple_strtoull(arg, &endp, 16);
-		if (endp == arg)
+	if (kstrtou64(arg, 0, value))
+		if (kstrtou64(arg, 16, value))
 			return KDB_BADINT;
-	}
-
-	*value = val;
-
 	return 0;
 }
 
@@ -483,10 +462,10 @@ int kdb_set(int argc, const char **argv)
 	 */
 	if (strcmp(argv[1], "KDBDEBUG") == 0) {
 		unsigned int debugflags;
-		char *cp;
+		int ret;
 
-		debugflags = simple_strtoul(argv[2], &cp, 0);
-		if (cp == argv[2] || debugflags & ~KDB_DEBUG_FLAG_MASK) {
+		ret = kstrtouint(argv[2], 0, &debugflags);
+		if (ret || debugflags & ~KDB_DEBUG_FLAG_MASK) {
 			kdb_printf("kdb: illegal debug flags '%s'\n",
 				    argv[2]);
 			return 0;
@@ -1631,10 +1610,10 @@ static int kdb_md(int argc, const char **argv)
 		if (!argv[0][3])
 			valid = 1;
 		else if (argv[0][3] == 'c' && argv[0][4]) {
-			char *p;
-			repeat = simple_strtoul(argv[0] + 4, &p, 10);
+			if (kstrtouint(argv[0] + 4, 10, &repeat))
+				return KDB_BADINT;
 			mdcount = ((repeat * bytesperword) + 15) / 16;
-			valid = !*p;
+			valid = 1;
 		}
 		last_repeat = repeat;
 	} else if (strcmp(argv[0], "md") == 0)
@@ -2095,15 +2074,11 @@ static int kdb_dmesg(int argc, const char **argv)
 	if (argc > 2)
 		return KDB_ARGCOUNT;
 	if (argc) {
-		char *cp;
-		lines = simple_strtol(argv[1], &cp, 0);
-		if (*cp)
+		if (kstrtoint(argv[1], 0, &lines))
 			lines = 0;
-		if (argc > 1) {
-			adjust = simple_strtoul(argv[2], &cp, 0);
-			if (*cp || adjust < 0)
+		if (argc > 1)
+			if (kstrtouint(argv[2], 0, &adjust) || adjust < 0)
 				adjust = 0;
-		}
 	}
 
 	/* disable LOGGING if set */
@@ -2440,14 +2415,12 @@ static int kdb_help(int argc, const char **argv)
 static int kdb_kill(int argc, const char **argv)
 {
 	long sig, pid;
-	char *endp;
 	struct task_struct *p;
 
 	if (argc != 2)
 		return KDB_ARGCOUNT;
 
-	sig = simple_strtol(argv[1], &endp, 0);
-	if (*endp)
+	if (kstrtol(argv[1], 0, &sig))
 		return KDB_BADINT;
 	if ((sig >= 0) || !valid_signal(-sig)) {
 		kdb_printf("Invalid signal parameter.<-signal>\n");
@@ -2455,8 +2428,7 @@ static int kdb_kill(int argc, const char **argv)
 	}
 	sig = -sig;
 
-	pid = simple_strtol(argv[2], &endp, 0);
-	if (*endp)
+	if (kstrtol(argv[2], 0, &pid))
 		return KDB_BADINT;
 	if (pid <= 0) {
 		kdb_printf("Process ID must be large than 0.\n");
-- 
2.25.1

Re: [PATCH 1/2] kdb: Replace the use of simple_strto with safer kstrto in kdb_main

[Doug Anderson]

Hi,

On Sun, Nov 19, 2023 at 4:07 PM Yuran Pereira <yuran.pereira@hotmail.com> wrote:
>
> The simple_str* family of functions perform no error checking in
> scenarios where the input value overflows the intended output variable.
> This results in these functions successfully returning even when the
> output does not match the input string.
>
> Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
> simple_strtoul(), and simple_strtoull() functions explicitly ignore
> overflows, which may lead to unexpected results in callers."
> Hence, the use of those functions is discouraged.
>
> This patch replaces all uses of the simple_strto* series of functions
> with their safer kstrto* alternatives.
>
> Side effects of this patch:
> - Every string to long or long long conversion using kstrto* is now
>   checked for failure.
> - kstrto* errors are handled with appropriate `KDB_BADINT` wherever
>   applicable.
> - A good side effect is that we end up saving a few lines of code
>   since unlike in simple_strto* functions, kstrto functions do not
>   need an additional "end pointer" variable, and the return values
>   of the latter can be directly checked in an "if" statement without
>   the need to define additional `ret` or `err` variables.
>   This, of course, results in cleaner, yet still easy to understand
>   code.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
>
> Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
> ---
>  kernel/debug/kdb/kdb_main.c | 70 +++++++++++--------------------------
>  1 file changed, 21 insertions(+), 49 deletions(-)

Sorry for taking so long to review this--it arrived in my inbox at a
bad time. A few minor nits below that I think should be fixed before
landing but overall I think it's a nice cleanup. Thanks!


> @@ -412,42 +412,21 @@ static void kdb_printenv(void)
>   */
>  int kdbgetularg(const char *arg, unsigned long *value)
>  {
> -       char *endp;
> -       unsigned long val;
> -
> -       val = simple_strtoul(arg, &endp, 0);
> -
> -       if (endp == arg) {
> -               /*
> -                * Also try base 16, for us folks too lazy to type the
> -                * leading 0x...
> -                */
> -               val = simple_strtoul(arg, &endp, 16);
> -               if (endp == arg)
> +       /*
> +        * If the first fails, also try base 16, for us
> +        * folks too lazy to type the leading 0x...
> +        */
> +       if (kstrtoul(arg, 0, value))
> +               if (kstrtoul(arg, 16, value))

Not new to your patch, but the above seems like a terrible idea to me.
What that means is that:

kdbgetularg("18", &value) => value is 18
kdbgetularg("19", &value) => value is 19
kdbgetularg("1a", &value) => value is 26

Bleh! If someone wants hex then they should put the 0x first.

I'd suggest a followup patch that removes the fallback for the lazy
folks. Here and in the next function...


> @@ -2095,15 +2074,11 @@ static int kdb_dmesg(int argc, const char **argv)
>         if (argc > 2)
>                 return KDB_ARGCOUNT;
>         if (argc) {
> -               char *cp;
> -               lines = simple_strtol(argv[1], &cp, 0);
> -               if (*cp)
> +               if (kstrtoint(argv[1], 0, &lines))
>                         lines = 0;
> -               if (argc > 1) {
> -                       adjust = simple_strtoul(argv[2], &cp, 0);
> -                       if (*cp || adjust < 0)
> +               if (argc > 1)
> +                       if (kstrtouint(argv[2], 0, &adjust) || adjust < 0)

My gut reaction is that some sort of build bot is going to come and
yell at you about the above line. Even if it doesn't, it's a bit
confusing. You're passing a pointer to an int into a function that
expects a pointer to an unsigned int. Most things don't really care
about signed/unsigned, but I could swear that some compilers get mad
when you start working with pointers to those types...

In any case, I think everything would work fine if you just change it
to kstrtoint(), right? I guess the other option would be to change the
variable to unsigned, but I guess that doesn't make sense since it's a
modifier to "lines" which is an int.

Side note: I didn't even know about the "adjust" argument, since it's
not in the help text in the command table below. I guess that could be
fixed in a separate patch.

nit: IMO if you have nested "if" statements then the outer one should
have braces. AKA:

if (a) {
  if (b)
    blah();
}

instead of:

if (a)
  if (b)
    blah();

...or you could do better and just change it to:

if (a && b)
  blah();

[PATCH 2/2] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

[Yuran Pereira]

The function simple_strtoul performs no error checking in scenarios
where the input value overflows the intended output variable.
This results in this function successfully returning, even when the
output does not match the input string (aka the function returns
successfully even when the result is wrong).

Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
simple_strtoul(), and simple_strtoull() functions explicitly ignore
overflows, which may lead to unexpected results in callers."
Hence, the use of those functions is discouraged.

This patch replaces all uses of the simple_strtoul with the safer
alternatives kstrtoint and kstrtol.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull

Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
---
 kernel/trace/trace_kdb.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 59857a1ee44c..3891f885e4a6 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -96,23 +96,21 @@ static int kdb_ftdump(int argc, const char **argv)
 {
 	int skip_entries = 0;
 	long cpu_file;
-	char *cp;
+	int err;
 	int cnt;
 	int cpu;
 
 	if (argc > 2)
 		return KDB_ARGCOUNT;
 
-	if (argc) {
-		skip_entries = simple_strtol(argv[1], &cp, 0);
-		if (*cp)
+	if (argc)
+		if (kstrtoint(argv[1], 0, &skip_entries))
 			skip_entries = 0;
-	}
 
 	if (argc == 2) {
-		cpu_file = simple_strtol(argv[2], &cp, 0);
-		if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
-		    !cpu_online(cpu_file))
+		err = kstrtol(argv[2], 0, &cpu_file);
+		if (err || cpu_file >= NR_CPUS || cpu_file < 0 ||
+				!cpu_online(cpu_file))
 			return KDB_BADINT;
 	} else {
 		cpu_file = RING_BUFFER_ALL_CPUS;
-- 
2.25.1

Re: [PATCH 2/2] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

[Doug Anderson]

Hi,

On Sun, Nov 19, 2023 at 4:10 PM Yuran Pereira <yuran.pereira@hotmail.com> wrote:
>
> The function simple_strtoul performs no error checking in scenarios
> where the input value overflows the intended output variable.
> This results in this function successfully returning, even when the
> output does not match the input string (aka the function returns
> successfully even when the result is wrong).
>
> Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
> simple_strtoul(), and simple_strtoull() functions explicitly ignore
> overflows, which may lead to unexpected results in callers."
> Hence, the use of those functions is discouraged.
>
> This patch replaces all uses of the simple_strtoul with the safer
> alternatives kstrtoint and kstrtol.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
>
> Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
> ---
>  kernel/trace/trace_kdb.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
> index 59857a1ee44c..3891f885e4a6 100644
> --- a/kernel/trace/trace_kdb.c
> +++ b/kernel/trace/trace_kdb.c
> @@ -96,23 +96,21 @@ static int kdb_ftdump(int argc, const char **argv)
>  {
>         int skip_entries = 0;
>         long cpu_file;
> -       char *cp;
> +       int err;
>         int cnt;
>         int cpu;
>
>         if (argc > 2)
>                 return KDB_ARGCOUNT;
>
> -       if (argc) {
> -               skip_entries = simple_strtol(argv[1], &cp, 0);
> -               if (*cp)
> +       if (argc)
> +               if (kstrtoint(argv[1], 0, &skip_entries))
>                         skip_entries = 0;
> -       }

Similar nit about braces as in patch #1. tl;dr is change the above to:

if (argc && kstrtoint(argv[1], 0, &skip_entries))
  skip_entries = 0;


>
>         if (argc == 2) {
> -               cpu_file = simple_strtol(argv[2], &cp, 0);
> -               if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
> -                   !cpu_online(cpu_file))
> +               err = kstrtol(argv[2], 0, &cpu_file);
> +               if (err || cpu_file >= NR_CPUS || cpu_file < 0 ||
> +                               !cpu_online(cpu_file))

nit: why did you change the indentation for "!cpu_online(cpu_file))"?
It seemed better before.

With nits fixed:

Reviewed-by: Douglas Anderson <dianders@chromium.org>

Re: [PATCH 2/2] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

[Daniel Thompson]

On Tue, Dec 05, 2023 at 01:41:57PM -0800, Doug Anderson wrote:
> Hi,
>
> On Sun, Nov 19, 2023 at 4:10 PM Yuran Pereira <yuran.pereira@hotmail.com> wrote:
> >
> > The function simple_strtoul performs no error checking in scenarios
> > where the input value overflows the intended output variable.
> > This results in this function successfully returning, even when the
> > output does not match the input string (aka the function returns
> > successfully even when the result is wrong).
> >
> > Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
> > simple_strtoul(), and simple_strtoull() functions explicitly ignore
> > overflows, which may lead to unexpected results in callers."
> > Hence, the use of those functions is discouraged.
> >
> > This patch replaces all uses of the simple_strtoul with the safer
> > alternatives kstrtoint and kstrtol.
> >
> > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
> >
> > Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
> > ---
> >  kernel/trace/trace_kdb.c | 14 ++++++--------
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
> > index 59857a1ee44c..3891f885e4a6 100644
> > --- a/kernel/trace/trace_kdb.c
> > +++ b/kernel/trace/trace_kdb.c
> > @@ -96,23 +96,21 @@ static int kdb_ftdump(int argc, const char **argv)
> >  {
> >         int skip_entries = 0;
> >         long cpu_file;
> > -       char *cp;
> > +       int err;
> >         int cnt;
> >         int cpu;
> >
> >         if (argc > 2)
> >                 return KDB_ARGCOUNT;
> >
> > -       if (argc) {
> > -               skip_entries = simple_strtol(argv[1], &cp, 0);
> > -               if (*cp)
> > +       if (argc)
> > +               if (kstrtoint(argv[1], 0, &skip_entries))
> >                         skip_entries = 0;
> > -       }
>
> Similar nit about braces as in patch #1. tl;dr is change the above to:
>
> if (argc && kstrtoint(argv[1], 0, &skip_entries))
>   skip_entries = 0;

Surely that should be:

if (...)
	return KDB_BADINT;

There seems little point switching to a "safer" API if we just ignore the
errors it provides us.


Daniel.

Re: [PATCH 2/2] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

[Doug Anderson]

Hi,

On Wed, Dec 6, 2023 at 3:38 AM Daniel Thompson
<daniel.thompson@linaro.org> wrote:
>
> On Tue, Dec 05, 2023 at 01:41:57PM -0800, Doug Anderson wrote:
> > Hi,
> >
> > On Sun, Nov 19, 2023 at 4:10 PM Yuran Pereira <yuran.pereira@hotmail.com> wrote:
> > >
> > > The function simple_strtoul performs no error checking in scenarios
> > > where the input value overflows the intended output variable.
> > > This results in this function successfully returning, even when the
> > > output does not match the input string (aka the function returns
> > > successfully even when the result is wrong).
> > >
> > > Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
> > > simple_strtoul(), and simple_strtoull() functions explicitly ignore
> > > overflows, which may lead to unexpected results in callers."
> > > Hence, the use of those functions is discouraged.
> > >
> > > This patch replaces all uses of the simple_strtoul with the safer
> > > alternatives kstrtoint and kstrtol.
> > >
> > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
> > >
> > > Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
> > > ---
> > >  kernel/trace/trace_kdb.c | 14 ++++++--------
> > >  1 file changed, 6 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
> > > index 59857a1ee44c..3891f885e4a6 100644
> > > --- a/kernel/trace/trace_kdb.c
> > > +++ b/kernel/trace/trace_kdb.c
> > > @@ -96,23 +96,21 @@ static int kdb_ftdump(int argc, const char **argv)
> > >  {
> > >         int skip_entries = 0;
> > >         long cpu_file;
> > > -       char *cp;
> > > +       int err;
> > >         int cnt;
> > >         int cpu;
> > >
> > >         if (argc > 2)
> > >                 return KDB_ARGCOUNT;
> > >
> > > -       if (argc) {
> > > -               skip_entries = simple_strtol(argv[1], &cp, 0);
> > > -               if (*cp)
> > > +       if (argc)
> > > +               if (kstrtoint(argv[1], 0, &skip_entries))
> > >                         skip_entries = 0;
> > > -       }
> >
> > Similar nit about braces as in patch #1. tl;dr is change the above to:
> >
> > if (argc && kstrtoint(argv[1], 0, &skip_entries))
> >   skip_entries = 0;
>
> Surely that should be:
>
> if (...)
>         return KDB_BADINT;
>
> There seems little point switching to a "safer" API if we just ignore the
> errors it provides us.

Ah, sure. I have no objections to that. Note that would have also been
possible with the old code, which did still do awkward error checking,
so I assumed that it was a conscious decision. ...but I'm definitely
happier with the error being reported instead of glossed over.

-Doug