[PATCH v1 1/1] lib/vsprintf: Check pointer before dereferencing in time_and_date()

[PATCH v1 1/1] lib/vsprintf: Check pointer before dereferencing in time_and_date()

[Andy Shevchenko]

The pointer may be invalid when gets to the printf(). In particular
the time_and_date() dereferencing it in some cases without checking.

Move the check from rtc_str() to time_and_date() to cover all cases.

Fixes: 7daac5b2fdf8 ("lib/vsprintf: Print time64_t in human readable format")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 lib/vsprintf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index e49f350ee549..3f99834fd788 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1928,9 +1928,6 @@ char *rtc_str(char *buf, char *end, const struct rtc_time *tm,
 	bool found = true;
 	int count = 2;
 
-	if (check_pointer(&buf, end, tm, spec))
-		return buf;
-
 	switch (fmt[count]) {
 	case 'd':
 		have_t = false;
@@ -1996,6 +1993,9 @@ static noinline_for_stack
 char *time_and_date(char *buf, char *end, void *ptr, struct printf_spec spec,
 		    const char *fmt)
 {
+	if (check_pointer(&buf, end, ptr, spec))
+		return buf;
+
 	switch (fmt[1]) {
 	case 'R':
 		return rtc_str(buf, end, (const struct rtc_time *)ptr, spec, fmt);
-- 
2.50.1

Re: [PATCH v1 1/1] lib/vsprintf: Check pointer before dereferencing in time_and_date()

[Petr Mladek]

On Mon 2025-11-10 14:21:18, Andy Shevchenko wrote:
> The pointer may be invalid when gets to the printf(). In particular
> the time_and_date() dereferencing it in some cases without checking.
> 
> Move the check from rtc_str() to time_and_date() to cover all cases.
> 
> Fixes: 7daac5b2fdf8 ("lib/vsprintf: Print time64_t in human readable format")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Great catch!

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

Re: [PATCH v1 1/1] lib/vsprintf: Check pointer before dereferencing in time_and_date()

[Petr Mladek]

On Mon 2025-11-10 14:21:18, Andy Shevchenko wrote:
> The pointer may be invalid when gets to the printf(). In particular
> the time_and_date() dereferencing it in some cases without checking.
> 
> Move the check from rtc_str() to time_and_date() to cover all cases.
> 
> Fixes: 7daac5b2fdf8 ("lib/vsprintf: Print time64_t in human readable format")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

JFYI, the patch has been comitted into printk/linux.git,
branch for-6.19.

Best Regards,
Petr