Re: [PATCH] x86: Fix earlyprintk ttyS2/3

[Daniel J Blueman]

On Tue, Apr 7, 2015 at 10:39 PM, Joe Perches <joe@xxxxxxxxxxx> wrote:
> On Tue, 2015-04-07 at 22:29 +0800, Daniel J Blueman wrote:
> >  Quite a few platforms use ttyS2 for their serial-over-LAN, so fix 
> > early
> >  printk support for ttyS2 and 3, avoiding the need to hard-code the 
> > IO port.
> []
> >  diff --git a/arch/x86/boot/early_serial_console.c 
> > b/arch/x86/boot/early_serial_console.c
> []
> >  @@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
> >   			else
> >   				pos = e - arg;
> >   		} else if (!strncmp(arg + pos, "ttyS", 4)) {
> >  -			static const int bases[] = { 0x3f8, 0x2f8 };
> >  -			int idx = 0;
> >  +			static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
> >  +			unsigned idx = 0;
> >
> >   			if (!strncmp(arg + pos, "ttyS", 4))
> >   				pos += 4;
> >
> >  -			if (arg[pos++] == '1')
> >  -				idx = 1;
> >  +			if ((arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
> >  +				idx = arg[pos] - '0';
>
> This doesn't prevent negative indexing in case someone
> does something like shift key typo "ttyS!" for "ttyS1".
>
> I've done that.

Gah; late night coding syndrome. Adding the missing cast in the first 
case only:

Subject: [PATCH v2] x86: Fix earlyprintk ttyS2/3

Quite a few platforms use ttyS2 for their serial-over-LAN, so fix early
printk support for ttyS2 and 3, avoiding the need to hard-code the IO 
port.

v2: Add missing unsigned cast to correct range check

Signed-off-by: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
---
arch/x86/boot/early_serial_console.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/early_serial_console.c 
b/arch/x86/boot/early_serial_console.c
index 5df2869..3d7f112 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
			else
				pos = e - arg;
		} else if (!strncmp(arg + pos, "ttyS", 4)) {
-			static const int bases[] = { 0x3f8, 0x2f8 };
+			static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
			int idx = 0;

			if (!strncmp(arg + pos, "ttyS", 4))
				pos += 4;

-			if (arg[pos++] == '1')
-				idx = 1;
+			if ((unsigned)(arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
+				idx = arg[pos] - '0';

+			pos++;
			port = bases[idx];
		}

--

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