netdev - [PATCH iproute2] ip: Fix size_columns() for very large values

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Date:   Mon, 27 Jun 2022 13:53:36 +0200
From:   Petr Machata <petrm@...dia.com>
To:     <netdev@...r.kernel.org>
CC:     Petr Machata <petrm@...dia.com>, Tariq Toukan <tariqt@...dia.com>,
        "Itay Aveksis" <itayav@...dia.com>
Subject: [PATCH iproute2] ip: Fix size_columns() for very large values

For values near the 64-bit boundary, the iterative application of
powi *= 10 causes powi to overflow without the termination condition of
powi >= val having ever been satisfied. Instead, when determining the
length of the number, iterate val /= 10 and terminate when it's a single
digit.

Fixes: 49437375b6c1 ("ip: dynamically size columns when printing stats")
CC: Tariq Toukan <tariqt@...dia.com>
CC: Itay Aveksis <itayav@...dia.com>
Signed-off-by: Petr Machata <petrm@...dia.com>
---
 ip/ipaddress.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 67403185..e0eb41bc 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -549,7 +549,7 @@ static void print_vfinfo(FILE *fp, struct ifinfomsg *ifi, struct rtattr *vfinfo)
 void size_columns(unsigned int cols[], unsigned int n, ...)
 {
 	unsigned int i, len;
-	uint64_t val, powi;
+	uint64_t val;
 	va_list args;
 
 	va_start(args, n);
@@ -560,7 +560,7 @@ void size_columns(unsigned int cols[], unsigned int n, ...)
 		if (human_readable)
 			continue;
 
-		for (len = 1, powi = 10; powi < val; len++, powi *= 10)
+		for (len = 1; val > 9; len++, val /= 10)
 			/* nothing */;
 		if (len > cols[i])
 			cols[i] = len;
-- 
2.35.3