lib/43937: S_*() macros in sys/stat.h are missing parenthesis

[avarab%gmail.com@localhost]

>Number:         43937
>Category:       lib
>Synopsis:       S_*() macros in sys/stat.h are missing parenthesis
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Oct 04 11:15:00 +0000 2010
>Originator:     Ævar Arnfjörð Bjarmason
>Release:        5.0.2
>Organization:
>Environment:
NetBSD conker 5.0.2 NetBSD 5.0.2 (GENERIC) #0: Sat Feb  6 13:44:19 UTC 2010  
builds%b8.netbsd.org@localhost:/home/builds/ab/netbsd-5-0-2-RELEASE/amd64/201002061851Z-obj/home/builds/ab/netbsd-5-0-2-RELEASE/src/sys/arch/amd64/compile/GENERIC
 amd64
>Description:
The S_*() macros in /usr/include/sys/stat.h don't apply parenthesis to
their arguments:

    $ grep '#define.*S_.*(m ' /usr/include/sys/stat.h
    #define S_ISDIR(m)      ((m & _S_IFMT) == _S_IFDIR)     /* directory */
    #define S_ISCHR(m)      ((m & _S_IFMT) == _S_IFCHR)     /* char special */
    #define S_ISBLK(m)      ((m & _S_IFMT) == _S_IFBLK)     /* block special */
    #define S_ISREG(m)      ((m & _S_IFMT) == _S_IFREG)     /* regular file */
    #define S_ISFIFO(m)     ((m & _S_IFMT) == _S_IFIFO)     /* fifo */
    #define S_ISLNK(m)      ((m & _S_IFMT) == _S_IFLNK)     /* symbolic link */
    #define S_ISSOCK(m)     ((m & _S_IFMT) == _S_IFSOCK)    /* socket */
    #define S_ISWHT(m)      ((m & _S_IFMT) == _S_IFWHT)     /* whiteout */

So calling e.g. S_ISREG(0644) means:

    S_IFREG | 0644 & _S_IFMT

On NetBSD but:

    (S_IFREG | 0644) & _S_IFMT

On Linux.

Since bitwise AND (&) has precedence over bitwise OR that introduces a
logic error.

>How-To-Repeat:
Look at /usr/include/sys/stat.h
>Fix:
You should put parenthesis around m to avoid this issue:

    $ grep S_ISREG /usr/include/sys/stat.h
    #define S_ISREG(m)      ((m & _S_IFMT) == _S_IFREG)     /* regular file */

    $ grep S_ISREG /usr/include/linux/stat.h
    #define S_ISREG(m)      (((m) & S_IFMT) == S_IFREG)