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setmode(): Use sysctl kern.proc.umask instead of umask() if possible.

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The kern.proc.umask.<pid> sysctl allows querying the umask without
temporarily modifying it.
This commit is contained in:
Jilles Tjoelker 2015-03-26 21:58:06 +00:00
parent 84233ddb80
commit 73cc817ec8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=280713
1 changed files with 33 additions and 9 deletions
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42
lib/libc/gen/setmode.c
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@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
#include "namespace.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <ctype.h>
#include <errno.h>
@ -68,6 +69,7 @@ typedef struct bitcmd {
#define CMD2_OBITS 0x08
#define CMD2_UBITS 0x10
static mode_t getumask(void);
static BITCMD *addcmd(BITCMD *, mode_t, mode_t, mode_t, mode_t);
static void compress_mode(BITCMD *);
#ifdef SETMODE_DEBUG
@ -169,7 +171,6 @@ setmode(const char *p)
int serrno;
char op, *ep;
BITCMD *set, *saveset, *endset;
sigset_t sigset, sigoset;
mode_t mask, perm, permXbits, who;
long perml;
int equalopdone;
@ -182,15 +183,9 @@ setmode(const char *p)
/*
* Get a copy of the mask for the permissions that are mask relative.
* Flip the bits, we want what's not set. Since it's possible that
* the caller is opening files inside a signal handler, protect them
* as best we can.
* Flip the bits, we want what's not set.
*/
sigfillset(&sigset);
(void)_sigprocmask(SIG_BLOCK, &sigset, &sigoset);
(void)umask(mask = umask(0));
mask = ~mask;
(void)_sigprocmask(SIG_SETMASK, &sigoset, NULL);
mask = ~getumask();
setlen = SET_LEN + 2;
@ -346,6 +341,35 @@ apply: if (!*p)
return NULL;
}
static mode_t
getumask(void)
{
sigset_t sigset, sigoset;
size_t len;
mode_t mask;
u_short smask;
/*
* First try requesting the umask without temporarily modifying it.
* Note that this does not work if the sysctl
* security.bsd.unprivileged_proc_debug is set to 0.
*/
len = sizeof(smask);
if (sysctl((int[4]){ CTL_KERN, KERN_PROC, KERN_PROC_UMASK, getpid() },
4, &smask, &len, NULL, 0) == 0)
return (smask);
/*
* Since it's possible that the caller is opening files inside a signal
* handler, protect them as best we can.
*/
sigfillset(&sigset);
(void)_sigprocmask(SIG_BLOCK, &sigset, &sigoset);
(void)umask(mask = umask(0));
(void)_sigprocmask(SIG_SETMASK, &sigoset, NULL);
return (mask);
}
static BITCMD *
addcmd(BITCMD *set, mode_t op, mode_t who, mode_t oparg, mode_t mask)
{