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login, mount: fix __SC_GETPW_R_SIZE_MAX usage 

sysconf(_SC_GETPW_R_SIZE_MAX) returns initial suggested size for pwd
buffer (see getpwnam_r man page or POSIX). This is not large enough in
some cases.

Yes, this sysconf option is misnamed (should be _SC_GETPW_R_SIZE_MIN).

Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2015-12-15 12:25:56 +01:00
parent b5febe0489
commit f7ac9e71b1
3 changed files with 17 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/c.h
View File

@ -346,4 +346,13 @@ static inline int xusleep(useconds_t usec)
# define UL_ASAN_BLACKLIST /* nothing */
#endif
/*
* Note that sysconf(_SC_GETPW_R_SIZE_MAX) returns *initial* suggested size for
* pwd buffer and in some cases it is not large enough. See POSIX and
* getpwnam_r man page for more details.
*/
#define UL_GETPW_BUFSIZ (16 * 1024)
#endif /* UTIL_LINUX_C_H */

25
libmount/src/utils.c
View File

@ -635,16 +635,6 @@ int mnt_get_filesystems(char ***filesystems, const char *pattern)
return rc;
}
static size_t get_pw_record_size(void)
{
#ifdef _SC_GETPW_R_SIZE_MAX
long sz = sysconf(_SC_GETPW_R_SIZE_MAX);
if (sz > 0)
return sz;
#endif
return 16384;
}
/*
* Returns an allocated string with username or NULL.
*/
@ -652,14 +642,13 @@ char *mnt_get_username(const uid_t uid)
{
struct passwd pwd;
struct passwd *res;
size_t sz = get_pw_record_size();
char *buf, *username = NULL;
buf = malloc(sz);
buf = malloc(UL_GETPW_BUFSIZ);
if (!buf)
return NULL;
if (!getpwuid_r(uid, &pwd, buf, sz, &res) && res)
if (!getpwuid_r(uid, &pwd, buf, UL_GETPW_BUFSIZ, &res) && res)
username = strdup(pwd.pw_name);
free(buf);
@ -671,17 +660,16 @@ int mnt_get_uid(const char *username, uid_t *uid)
int rc = -1;
struct passwd pwd;
struct passwd *pw;
size_t sz = get_pw_record_size();
char *buf;
if (!username || !uid)
return -EINVAL;
buf = malloc(sz);
buf = malloc(UL_GETPW_BUFSIZ);
if (!buf)
return -ENOMEM;
if (!getpwnam_r(username, &pwd, buf, sz, &pw) && pw) {
if (!getpwnam_r(username, &pwd, buf, UL_GETPW_BUFSIZ, &pw) && pw) {
*uid= pw->pw_uid;
rc = 0;
} else {
@ -699,17 +687,16 @@ int mnt_get_gid(const char *groupname, gid_t *gid)
int rc = -1;
struct group grp;
struct group *gr;
size_t sz = get_pw_record_size();
char *buf;
if (!groupname || !gid)
return -EINVAL;
buf = malloc(sz);
buf = malloc(UL_GETPW_BUFSIZ);
if (!buf)
return -ENOMEM;
if (!getgrnam_r(groupname, &grp, buf, sz, &gr) && gr) {
if (!getgrnam_r(groupname, &grp, buf, UL_GETPW_BUFSIZ, &gr) && gr) {
*gid= gr->gr_gid;
rc = 0;
} else {

12
login-utils/login.c
View File

@ -674,22 +674,14 @@ static struct passwd *get_passwd_entry(const char *username,
struct passwd *pwd)
{
struct passwd *res = NULL;
size_t sz = 16384;
int x;
if (!pwdbuf || !username)
return NULL;
#ifdef _SC_GETPW_R_SIZE_MAX
{
long xsz = sysconf(_SC_GETPW_R_SIZE_MAX);
if (xsz > 0)
sz = (size_t) xsz;
}
#endif
*pwdbuf = xrealloc(*pwdbuf, sz);
*pwdbuf = xrealloc(*pwdbuf, UL_GETPW_BUFSIZ);
x = getpwnam_r(username, pwd, *pwdbuf, sz, &res);
x = getpwnam_r(username, pwd, *pwdbuf, UL_GETPW_BUFSIZ, &res);
if (!res) {
errno = x;
return NULL;