Re: [PATCH] fb: sm501fb off-by-1 sysfs store
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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2007-03-01 13:25:58
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On Thu, 1 Mar 2007, Paul Mundt wrote:
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.
sizeof("string") is great for making sure you have space in your buffer,
but rather less so for string comparisons :-)quoted hunk ↗ jump to hunk
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; else return -EINVAL;
What about using just `strlen("string")' instead? ISTR gcc optimizes this to a
constant. Not that it matters that much, as the actual string won't be
duplicated.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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