linux-kernel - [RFC PATCH 3/3] lib/vsprintf.c: increase the size of the field

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Date:	Wed, 16 Sep 2015 11:08:43 +0200
From:	Maurizio Lombardi <mlombard@...hat.com>
To:	tj@...nel.org
Cc:	joe@...ches.com, linux@...musvillemoes.dk,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/3] lib/vsprintf.c: increase the size of the field_width variable

When printing a bitmap using the "%*pb[l]" printk format
a 16 bit variable (field_width) is used to store the size of the bitmap.
In some cases 16 bits are not sufficient, the variable overflows and
printk does not work as expected.

This patch fixes the problem by changing the type of field_width to s32.

How to reproduce the bug:

1.load scsi_debug
# modprobe scsi-debug dev_size_mb=256 lbpu=1 lbpws10=1

2.create VG
# vgcreate tsvg /dev/sdb
  Physical volume "/dev/sdb" successfully created
  Volume group "tsvg" successfully created

3. Bitmap should be set, but still empty
# cat /sys/bus/pseudo/drivers/scsi_debug/map

Expected results:
# cat /sys/bus/pseudo/drivers/scsi_debug/map
0-15

Signed-off-by: Maurizio Lombardi <mlombard@...hat.com>
---
 lib/vsprintf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index f49bf54..9712260 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -384,8 +384,8 @@ struct printf_spec {
 	u8	flags;		/* flags to number() */
 	u8	base;		/* number base, 8, 10 or 16 only */
 	u8	qualifier;	/* number qualifier, one of 'hHlLtzZ' */
-	s16	field_width;	/* width of output field */
 	s16	precision;	/* # of digits/chars */
+	s32	field_width;	/* width of output field */
 };
 
 static noinline_for_stack
-- 
Maurizio Lombardi

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