linux-kernel - [PATCH] char/mwave: Adjust io port register size

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Message-Id: <20211203084206.3104326-1-keescook@chromium.org>
Date:   Fri,  3 Dec 2021 00:42:06 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] char/mwave: Adjust io port register size

Using MKWORD() on a byte-sized variable results in OOB read. Expand the
size of the reserved area so both MKWORD and MKBYTE continue to work
without overflow. Silences this warning on a -Warray-bounds build:

drivers/char/mwave/3780i.h:346:22: error: array subscript 'short unsigned int[0]' is partly outside array bounds of 'DSP_ISA_SLAVE_CONTROL[1]' [-Werror=array-bounds]
  346 | #define MKWORD(var) (*((unsigned short *)(&var)))
      |                     ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/char/mwave/3780i.h:356:40: note: in definition of macro 'OutWordDsp'
  356 | #define OutWordDsp(index,value)   outw(value,usDspBaseIO+index)
      |                                        ^~~~~
drivers/char/mwave/3780i.c:373:41: note: in expansion of macro 'MKWORD'
  373 |         OutWordDsp(DSP_IsaSlaveControl, MKWORD(rSlaveControl));
      |                                         ^~~~~~
drivers/char/mwave/3780i.c:358:31: note: while referencing 'rSlaveControl'
  358 |         DSP_ISA_SLAVE_CONTROL rSlaveControl;
      |                               ^~~~~~~~~~~~~

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/char/mwave/3780i.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/mwave/3780i.h b/drivers/char/mwave/3780i.h
index 9ccb6b270b07..95164246afd1 100644
--- a/drivers/char/mwave/3780i.h
+++ b/drivers/char/mwave/3780i.h
@@ -68,7 +68,7 @@ typedef struct {
 	unsigned char ClockControl:1;	/* RW: Clock control: 0=normal, 1=stop 3780i clocks */
 	unsigned char SoftReset:1;	/* RW: Soft reset 0=normal, 1=soft reset active */
 	unsigned char ConfigMode:1;	/* RW: Configuration mode, 0=normal, 1=config mode */
-	unsigned char Reserved:5;	/* 0: Reserved */
+	unsigned short Reserved:13;	/* 0: Reserved */
 } DSP_ISA_SLAVE_CONTROL;
 
 
-- 
2.30.2