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From: Paul Mundt <>
To: Ben Dooks <>
Subject: [PATCH] fb: sm501fb off-by-1 sysfs store
Date: Thu, 1 Mar 2007 17:24:56 +0900	[thread overview]
Message-ID: <> (raw)

Currently sm501fb_crtsrc_store() won't allow the routing to be changed
via echos from userspace in to the sysfs file. The reason for this is
that the strnicmp() for both heads uses a sizeof() for the string length,
which ends up being strlen() + 1 (\0 in the normal case, but the echo
gives a newline, which is where the issue occurs), this then causes a
mismatch and subsequently bails with the -EINVAL.

In addition to this, the hardcoded lengths were then used for the store
length that was returned, which ended up being erroneous and resulting in
a write error. There's also no point in returning anything but the full
length since it will -EINVAL out on a mismatch well before then anyways.

sizeof("string") is great for making sure you have space in your buffer,
but rather less so for string comparisons :-)

Signed-off-by: Paul Mundt <>


 drivers/video/sm501fb.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/video/sm501fb.c b/drivers/video/sm501fb.c
index 02b290c..72b5358 100644
--- a/drivers/video/sm501fb.c
+++ b/drivers/video/sm501fb.c
@@ -1074,9 +1074,9 @@ static ssize_t sm501fb_crtsrc_store(struct device *dev,
 	if (len < 1)
 		return -EINVAL;
-	if (strnicmp(buf, "crt", sizeof("crt")) == 0)
+	if (strnicmp(buf, "crt", 3) == 0)
 		head = HEAD_CRT;
-	else if (strnicmp(buf, "panel", sizeof("panel")) == 0)
+	else if (strnicmp(buf, "panel", 5) == 0)
 		head = HEAD_PANEL;
 		return -EINVAL;
@@ -1098,7 +1098,7 @@ static ssize_t sm501fb_crtsrc_store(struct device *dev,
 	writel(ctrl, info->regs + SM501_DC_CRT_CONTROL);
-	return (head == HEAD_CRT) ? 3 : 5;
+	return len;
 /* Prepare the device_attr for registration with sysfs later */

             reply	other threads:[~2007-03-01  8:27 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-03-01  8:24 Paul Mundt [this message]
2007-03-01  9:16 ` Ben Dooks
2007-03-01 13:25 ` [Linux-fbdev-devel] " Geert Uytterhoeven
2007-03-01 13:35   ` Paul Mundt

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