[PATCH v7 10/11] lib: sbi: Fix timing of clearing tbuf

[Xiang W]

A single scan of the format char may add multiple characters to the
tbuf, causing a buffer overflow. You should check if tbuf is full in
printc so that it does not cause a buffer overflow.

Signed-off-by: Xiang W <wxjstz at 126.com>
---
 lib/sbi/sbi_console.c | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/lib/sbi/sbi_console.c b/lib/sbi/sbi_console.c
index af5e94b..50af405 100644
--- a/lib/sbi/sbi_console.c
+++ b/lib/sbi/sbi_console.c
@@ -121,6 +121,7 @@ unsigned long sbi_ngets(char *str, unsigned long len)
 #define PAD_ZERO 2
 #define PAD_ALTERNATE 4
 #define PAD_SIGN 8
+#define USED_TBUF (1 << (8 * sizeof(int) - 1))
 #define PRINT_BUF_LEN 64
 
 #define va_start(v, l) __builtin_va_start((v), l)
@@ -128,7 +129,7 @@ unsigned long sbi_ngets(char *str, unsigned long len)
 #define va_arg __builtin_va_arg
 typedef __builtin_va_list va_list;
 
-static void printc(char **out, u32 *out_len, char ch)
+static void printc(char **out, u32 *out_len, char ch, int flags)
 {
 	if (!out) {
 		sbi_putc(ch);
@@ -142,8 +143,14 @@ static void printc(char **out, u32 *out_len, char ch)
 	if (!out_len || *out_len > 1) {
 		*(*out)++ = ch;
 		**out = '\0';
-		if (out_len)
+		if (out_len) {
 			--(*out_len);
+			if ((flags & USED_TBUF) && *out_len == 1) {
+				nputs_all(console_tbuf, CONSOLE_TBUF_MAX - *out_len);
+				*out = console_tbuf;
+				*out_len = CONSOLE_TBUF_MAX;
+			}
+		}
 	}
 }
 
@@ -154,16 +161,16 @@ static int prints(char **out, u32 *out_len, const char *string, int width,
 	width -= sbi_strlen(string);
 	if (!(flags & PAD_RIGHT)) {
 		for (; width > 0; --width) {
-			printc(out, out_len, flags & PAD_ZERO ? '0' : ' ');
+			printc(out, out_len, flags & PAD_ZERO ? '0' : ' ', flags);
 			++pc;
 		}
 	}
 	for (; *string; ++string) {
-		printc(out, out_len, *string);
+		printc(out, out_len, *string, flags);
 		++pc;
 	}
 	for (; width > 0; --width) {
-		printc(out, out_len, ' ');
+		printc(out, out_len, ' ', flags);
 		++pc;
 	}
 
@@ -215,18 +222,18 @@ static int printi(char **out, u32 *out_len, long long i,
 
 	if (flags & PAD_ZERO) {
 		if (sign) {
-			printc(out, out_len, sign);
+			printc(out, out_len, sign, flags);
 			++pc;
 			--width;
 		}
 		if (i && (flags & PAD_ALTERNATE)) {
 			if (b == 16 || b == 8) {
-				printc(out, out_len, '0');
+				printc(out, out_len, '0', flags);
 				++pc;
 				--width;
 			}
 			if (b == 16) {
-				printc(out, out_len, 'x' - 'a' + letbase);
+				printc(out, out_len, 'x' - 'a' + letbase, flags);
 				++pc;
 				--width;
 			}
@@ -265,15 +272,11 @@ static int print(char **out, u32 *out_len, const char *format, va_list args)
 	}
 
 	for (; *format != 0; ++format) {
-		if (use_tbuf && !console_tbuf_len) {
-			nputs_all(console_tbuf, CONSOLE_TBUF_MAX);
-			console_tbuf_len = CONSOLE_TBUF_MAX;
-			tout = console_tbuf;
-		}
-
+		width = flags = 0;
+		if (use_tbuf)
+			flags |= USED_TBUF;
 		if (*format == '%') {
 			++format;
-			width = flags = 0;
 			if (*format == '\0')
 				break;
 			if (*format == '%')
@@ -371,7 +374,7 @@ static int print(char **out, u32 *out_len, const char *format, va_list args)
 			}
 		} else {
 literal:
-			printc(out, out_len, *format);
+			printc(out, out_len, *format, flags);
 			++pc;
 		}
 	}
-- 
2.40.1