[PATCH v4 0/3] Replace the use of simple_strtol/ul functions with kstrto

[PATCH v4 0/3] Replace the use of simple_strtol/ul functions with kstrto

[Nir Lichtman]

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
Nir Lichtman (1):
  kdb: Remove fallback interpretation of arbitrary numbers as hex

This patch is originally based upon
https://lore.kernel.org/all/GV1PR10MB65635561FB160078C3744B5FE8B4A@GV1PR10MB6563.EURPRD10.PROD.OUTLOOK.COM/

Since the original thread was left with a review and the comments have not been addressed,
decided to continue the minor work left to move this patch forward.

v2:
- Styling fixes
- Fix an invalid conversion to unsigned int instead of signed as it was supposed to be
- Fix one of the conversions to return an error in case of failure, instead of silently falling back to a default value
- Add Douglas's suggestion for removing the hex interpretation fallback
v3: 
- Split to 3 parts instead of 2 (in which the 3rd part now contains the hex interpretation fix)
- Fix the patch series to properly reference the cover
- Fix credit tags
v4:
- Fix regression between v2 to v3 in which I accidentaly
reverted an improper unsigned/signed conversion
- Fix nit of spacing in if condition parens split into multiple lines


 kernel/debug/kdb/kdb_main.c | 69 +++++++++--------------------------
 kernel/trace/trace_kdb.c    | 15 +++-----
 2 files changed, 23 insertions(+), 61 deletions(-)
--
2.39.2

[PATCH v4 1/3] kdb: Replace the use of simple_strto with safer kstrto in kdb_main

[Nir Lichtman]

From: Yuran Pereira <yuran.pereira@hotmail.com>

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>
[nir: addressed review comments by fixing styling, invalid conversion and a missing error return]
Signed-off-by: Nir Lichtman <nir@lichtman.org>
---
 kernel/debug/kdb/kdb_main.c | 69 +++++++++++--------------------------
 1 file changed, 21 insertions(+), 48 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index f5f7d7fb5936..f8703ab760d9 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -306,8 +306,8 @@ 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;
 }
@@ -402,42 +402,23 @@ 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;
 }
 
@@ -473,10 +454,10 @@ 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;
@@ -1619,10 +1600,10 @@ 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)
@@ -2083,15 +2064,10 @@ 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)
-				adjust = 0;
-		}
+		if (argc > 1 && (kstrtoint(argv[2], 0, &adjust) || adjust < 0))
+			adjust = 0;
 	}
 
 	/* disable LOGGING if set */
@@ -2428,14 +2404,12 @@ 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");
@@ -2443,8 +2417,7 @@ 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");
-- 
2.39.2

Re: [PATCH v4 1/3] kdb: Replace the use of simple_strto with safer kstrto in kdb_main

[Doug Anderson]

Hi,

On Mon, Oct 28, 2024 at 12:19 PM Nir Lichtman <nir@lichtman.org> wrote:
>
> From: Yuran Pereira <yuran.pereira@hotmail.com>
>
> 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>
> [nir: addressed review comments by fixing styling, invalid conversion and a missing error return]
> Signed-off-by: Nir Lichtman <nir@lichtman.org>
> ---
>  kernel/debug/kdb/kdb_main.c | 69 +++++++++++--------------------------
>  1 file changed, 21 insertions(+), 48 deletions(-)

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

[PATCH v4 2/3] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

[Nir Lichtman]

From: Yuran Pereira <yuran.pereira@hotmail.com>

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>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
[nir: style fixes]
Signed-off-by: Nir Lichtman <nir@lichtman.org>
---
 kernel/trace/trace_kdb.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 59857a1ee44c..1e72d20b3c2f 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -96,22 +96,19 @@ 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)
-			skip_entries = 0;
-	}
+	if (argc && kstrtoint(argv[1], 0, &skip_entries))
+		return KDB_BADINT;
 
 	if (argc == 2) {
-		cpu_file = simple_strtol(argv[2], &cp, 0);
-		if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
+		err = kstrtol(argv[2], 0, &cpu_file);
+		if (err || cpu_file >= NR_CPUS || cpu_file < 0 ||
 		    !cpu_online(cpu_file))
 			return KDB_BADINT;
 	} else {
-- 
2.39.2

[PATCH v4 3/3] kdb: Remove fallback interpretation of arbitrary numbers as hex

[Nir Lichtman]

Remove logic that enables a fallback of interpreting numbers supplied in KDB CLI
to be interpreted as hex without explicit "0x" prefix as this can be confusing
for the end users.

Suggested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Nir Lichtman <nir@lichtman.org>
---
 kernel/debug/kdb/kdb_main.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index f8703ab760d9..5f4be507d79f 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -402,23 +402,15 @@ static void kdb_printenv(void)
  */
 int kdbgetularg(const char *arg, unsigned long *value)
 {
-	/*
-	 * 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;
-	}
+	if (kstrtoul(arg, 0, value))
+		return KDB_BADINT;
 	return 0;
 }
 
 int kdbgetu64arg(const char *arg, u64 *value)
 {
-	if (kstrtou64(arg, 0, value)) {
-		if (kstrtou64(arg, 16, value))
-			return KDB_BADINT;
-	}
+	if (kstrtou64(arg, 0, value))
+		return KDB_BADINT;
 	return 0;
 }
 
-- 
2.39.2

Re: [PATCH v4 0/3] Replace the use of simple_strtol/ul functions with kstrto

[Daniel Thompson]

On Mon, 28 Oct 2024 19:17:00 +0000, Nir Lichtman 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 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.
> 
> [...]

Applied, thanks!

[1/3] kdb: Replace the use of simple_strto with safer kstrto in kdb_main
      commit: fe0c87871fc0b97f6d374b670c81f7c4087eebc5
[2/3] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump
      commit: c56642c737fc0bd9bcc3a22a2bf8ed6f5900a660
[3/3] kdb: Remove fallback interpretation of arbitrary numbers as hex
      commit: 5f4ca702e36893a276fccb0aa55ab36e19dfbb50

Best regards,
-- 
Daniel Thompson <daniel.thompson@linaro.org>

Re: [PATCH v4 0/3] Replace the use of simple_strtol/ul functions with kstrto

[Nir Lichtman]

On Fri, Nov 08, 2024 at 08:38:35AM +0000, Daniel Thompson wrote:
> 
> On Mon, 28 Oct 2024 19:17:00 +0000, Nir Lichtman 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 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.
> > 
> > [...]
> 
> Applied, thanks!

Thanks!

Nir