From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: Thu, 26 Mar 2026 12:12:00 +0000 (+0900)
Subject: lib/vsprintf: Fix to check field_width and precision
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=71876dffab295b6e25d4209f0424da8fc5020e12;p=thirdparty%2Fkernel%2Flinux.git

lib/vsprintf: Fix to check field_width and precision

Check the field_width and presition correctly. Previously it depends
on the bitfield conversion from int to check out-of-range error.
However, commit 938df695e98d ("vsprintf: associate the format state
with the format pointer") changed those fields to int.
We need to check the out-of-range correctly without bitfield
conversion.

Fixes: 938df695e98d ("vsprintf: associate the format state with the format pointer")
Reported-by: David Laight <david.laight.linux@gmail.com>
Closes: https://lore.kernel.org/all/20260318151250.40fef0ab@pumpkin/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/177452712047.197965.16376597502504928495.stgit@devnote2
Signed-off-by: Petr Mladek <pmladek@suse.com>
---

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 9f359b31c8d1c..3c76cc5c7f9ce 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2640,6 +2640,18 @@ static unsigned char spec_flag(unsigned char c)
 	return (c < sizeof(spec_flag_array)) ? spec_flag_array[c] : 0;
 }
 
+static void set_field_width(struct printf_spec *spec, int width)
+{
+	spec->field_width = clamp(width, -FIELD_WIDTH_MAX, FIELD_WIDTH_MAX);
+	WARN_ONCE(spec->field_width != width, "field width %d out of range", width);
+}
+
+static void set_precision(struct printf_spec *spec, int prec)
+{
+	spec->precision = clamp(prec, 0, PRECISION_MAX);
+	WARN_ONCE(spec->precision < prec, "precision %d too large", prec);
+}
+
 /*
  * Helper function to decode printf style format.
  * Each call decode a token from the format and return the
@@ -2710,7 +2722,7 @@ struct fmt format_decode(struct fmt fmt, struct printf_spec *spec)
 	spec->field_width = -1;
 
 	if (isdigit(*fmt.str))
-		spec->field_width = skip_atoi(&fmt.str);
+		set_field_width(spec, skip_atoi(&fmt.str));
 	else if (unlikely(*fmt.str == '*')) {
 		/* it's the next argument */
 		fmt.state = FORMAT_STATE_WIDTH;
@@ -2724,9 +2736,7 @@ precision:
 	if (unlikely(*fmt.str == '.')) {
 		fmt.str++;
 		if (isdigit(*fmt.str)) {
-			spec->precision = skip_atoi(&fmt.str);
-			if (spec->precision < 0)
-				spec->precision = 0;
+			set_precision(spec, skip_atoi(&fmt.str));
 		} else if (*fmt.str == '*') {
 			/* it's the next argument */
 			fmt.state = FORMAT_STATE_PRECISION;
@@ -2799,24 +2809,6 @@ qualifier:
 	return fmt;
 }
 
-static void
-set_field_width(struct printf_spec *spec, int width)
-{
-	spec->field_width = width;
-	if (WARN_ONCE(spec->field_width != width, "field width %d too large", width)) {
-		spec->field_width = clamp(width, -FIELD_WIDTH_MAX, FIELD_WIDTH_MAX);
-	}
-}
-
-static void
-set_precision(struct printf_spec *spec, int prec)
-{
-	spec->precision = prec;
-	if (WARN_ONCE(spec->precision != prec, "precision %d too large", prec)) {
-		spec->precision = clamp(prec, 0, PRECISION_MAX);
-	}
-}
-
 /*
  * Turn a 1/2/4-byte value into a 64-bit one for printing: truncate
  * as necessary and deal with signedness.