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* Copyright © W. Michael Petullo <mike@flyn.org>, 2004
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* Copyright © Jan Engelhardt, 2005-2011
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* Copyright © Bastian Kleineidam <calvin [at] debian org>, 2005
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* This file is part of pam_mount; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public License
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* as published by the Free Software Foundation; either version 2.1
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* of the License, or (at your option) any later version.
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pmvarrun.c -- Updates /run/pam_mount/<user>.
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A seperate program is needed so that /run/pam_mount/<user> may be
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created with a pam_mount-specific security context (otherwise SELinux
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policy will conflict with whatever called pam_mount.so).
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#include <sys/types.h>
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#include <libHX/defs.h>
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#include <libHX/string.h>
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#include "libcryptmount.h"
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#include "pam_mount.h"
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#define ASCIIZ_LLX sizeof("0xFFFFFFFF""FFFFFFFF")
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#define VAR_RUN_PMT RUNDIR "/pam_mount"
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static int create_var_run(void);
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static int modify_pm_count(const char *, long);
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static int open_and_lock(const char *, long);
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static void parse_args(const int, const char **, struct settings *);
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static long read_current_count(int, const char *);
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static void set_defaults(struct settings *);
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static void usage(int, const char *);
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static int write_count(int, long, const char *);
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static unsigned int pmvr_debug;
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* usage - display help
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* @exitcode: numeric value we will be exiting with
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* @error: descriptive error string
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* Displays the help string and an optional extra error message.
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static void usage(const int exitcode, const char *error)
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fprintf(stderr, "Usage: pmvarrun -u USER [-o NUMBER] [-d]\n");
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fprintf(stderr, "%s\n\n", error);
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* @settings: pointer to settings structure
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static void set_defaults(struct settings *settings)
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settings->user = NULL;
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settings->operation = 1;
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if ((s = getenv("_PMT_DEBUG_LEVEL")) != NULL &&
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strtoul(s, NULL, 0) != 0) {
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ehd_logctl(EHD_LOGFT_DEBUG, EHD_LOG_SET);
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* from git://dev.medozas.de/vitalnix /src/libvxutil/util.c
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static bool valid_username(const char *n)
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* Note to future editors: Some systems disallow leading digits for
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* usernames. Possibly because it is concerned about badly-written
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* programs detecting numeric UIDs by merely doing
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* strtoul(s, &e, 0) && s != e, which falls victim to usernames
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* with leading digits.
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* So pam_mount, in its original form at least (distros can patch
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* their copy up as they see fit), should at best reject
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* leading digits too.
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* Cannot use isalpha/isdigit here since that may include
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if (!((*n >= 'A' && *n <= 'Z') || (*n >= 'a' && *n <= 'z') ||
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if (*n == '$' && *(n+1) == '\0') /* Samba accounts */
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valid = (*n >= 'A' && *n <= 'Z') || (*n >= 'a' && *n <= 'z') ||
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(*n >= '0' && *n <= '9') || *n == '_' || *n == '.' ||
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*n == '-' || *n == ' ' || *n == '\\';
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* @n: string to analyze
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* Calls @strtol on @n using base 10 and makes sure there were no invalid
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* characters in @n. Returns the value, or %LONG_MAX in case of an
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* NOTE: This function is only referenced from pmvarrun.c.
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long str_to_long(const char *n)
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l0g("count string is NULL\n");
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val = strtol(n, &endptr, 10);
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if (*endptr != '\0') {
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l0g("count string is not valid\n");
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* @argc: number of elements in @argv
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* @argv: NULL-terminated argument vector
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* @settings: pointer to settings structure
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* Parse options from @argv and put it into @settings.
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static void parse_args(int argc, const char **argv, struct settings *settings)
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while ((c = getopt(argc, const_cast2(char * const *, argv),
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usage(EXIT_SUCCESS, NULL);
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ehd_logctl(EHD_LOGFT_DEBUG, EHD_LOG_SET);
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settings->operation = str_to_long(optarg);
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if (settings->operation == LONG_MAX ||
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settings->operation == LONG_MIN)
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usage(EXIT_FAILURE, "count string is not valid");
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if (!valid_username(optarg)) {
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fprintf(stderr, "Invalid user name\n");
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if ((settings->user = HX_strdup(optarg)) == NULL)
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usage(EXIT_FAILURE, NULL);
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* @user: user to poke on
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* @amount: increment (usually -1, 0 or +1)
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* Adjusts /var/run/pam_mount/@user by @amount, or deletes the file if the
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* resulting value (current + @amount) is <= 0. Returns >= 0 on success to
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* indicate the new login count, or negative to indicate errno. -ESTALE and
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* -EOVERFLOW are passed up from subfunctions and must be handled in the
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static int modify_pm_count(const char *user, long amount)
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char filename[PATH_MAX + 1];
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assert(user != NULL);
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if ((pent = getpwnam(user)) == NULL) {
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l0g("could not resolve user %s\n", user);
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if (stat(VAR_RUN_PMT, &sb) < 0) {
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if (errno != ENOENT) {
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l0g("unable to stat " VAR_RUN_PMT ": %s\n",
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if ((ret = create_var_run()) < 0)
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snprintf(filename, sizeof(filename), VAR_RUN_PMT "/%s", user);
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while ((ret = fd = open_and_lock(filename, pent->pw_uid)) == -EAGAIN)
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if ((val = read_current_count(fd, filename)) < 0) {
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w4rn("parsed count value %ld\n", val);
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/* amount == 0 implies query */
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ret = write_count(fd, val + amount, filename);
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return (ret < 0) ? ret : val + amount;
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int main(int argc, const char **argv)
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struct settings settings;
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ehd_logctl(EHD_LOGFT_NOSYSLOG, EHD_LOG_SET);
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set_defaults(&settings);
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parse_args(argc, argv, &settings);
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if (settings.user == NULL)
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usage(EXIT_FAILURE, NULL);
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ret = modify_pm_count(settings.user, settings.operation);
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if (ret == -ESTALE) {
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} else if (ret < 0) {
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/* print current count so pam_mount module may read it */
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//-----------------------------------------------------------------------------
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* Creates the /run/pam_mount directory required by pmvarrun and sets
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* proper permissions on it.
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* Returns >0 for success or <=0 to indicate errno.
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static int create_var_run(void)
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static const unsigned int mode = S_IRUGO | S_IXUGO | S_IWUSR;
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w4rn("creating " VAR_RUN_PMT);
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if (HX_mkdir(VAR_RUN_PMT, mode) < 0) {
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l0g("unable to create " VAR_RUN_PMT ": %s\n", strerror(errno));
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if (chown(VAR_RUN_PMT, 0, 0) < 0) {
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l0g("unable to chown " VAR_RUN_PMT ": %s\n", strerror(errno));
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* 0755: `su` creates file group owned by user and then releases root
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* permissions. User needs to be able to access file on logout.
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if (chmod(VAR_RUN_PMT, mode) < 0) {
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l0g("unable to chmod " VAR_RUN_PMT ": %s\n", strerror(errno));
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* @filename: file to open
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* Creates if necessary, opens and chown()s @filename, and locks it.
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* Returns the fd if all of that succeeded, -EAGAIN if the file was unlinked
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* during operation (see below), -ESTALE if the lock could not be obtained,
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* and <0 otherwise to indicate errno.
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static int open_and_lock(const char *filename, long uid) {
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struct flock lockinfo = {
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.l_whence = SEEK_SET,
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if ((fd = open(filename, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR)) < 0) {
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l0g("unable to open %s: %s\n", filename, strerror(errno));
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if (fchown(fd, uid, 0) < 0) {
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l0g("unable to chown %s: %s\n", filename, strerror(errno));
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* Note: Waiting too long might interfere with LOGIN_TIMEOUT from
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* /etc/login.defs, and /bin/login itself may prematurely kill the
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ret = fcntl(fd, F_SETLKW, &lockinfo);
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* [Flyn] If someone has locked the file and not written to it
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* in at least 20 seconds, we assume they either forgot to
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* unlock it or are catatonic -- chances are slim that they are
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* in the middle of a read-write cycle and I do not want to
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* make us lock users out. Perhaps I should just return
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* %PAM_SUCCESS instead and log the event? Kill the process
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* holding the lock? Options abound... For now, we ignore it.
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* [CCJ] pmvarrun is the only one ever writing to that file,
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* and we keep the lock as short as possible. So if there is no
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* response within the time limit, something is fouled up (e.g.
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* NFS server not responding -- though /var/run should at best
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* not be on an NFS mount). Continue, let user log in, do not
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w4rn("stale lock on file %s - continuing without increasing"
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"pam_mount reference count\n", filename);
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* It is possible at this point that the file has been removed by a
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* previous login; if this happens, we need to start over.
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if (stat(filename, &sb) < 0) {
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* read_current_count -
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* @fd: file descriptor to read from
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* Reads the current user's reference count from @fd and returns the value
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* on success. Otherwise, returns -EOVERFLOW in case we suspect a problem or
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* <0 to indicate errno.
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static long read_current_count(int fd, const char *filename) {
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char buf[ASCIIZ_LLX] = {};
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if ((ret = read(fd, buf, sizeof(buf))) < 0) {
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l0g("read error on %s: %s\n", filename, strerror(errno));
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} else if (ret == 0) {
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/* File is empty, ret is already 0 -- we are set. */
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} else if (ret < sizeof(buf)) {
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if ((ret = strtol(buf, &p, 0)) >= LONG_MAX || p == buf) {
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l0g("parse problem / session count corrupt "
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"(overflow), check your refcount file\n");
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} else if (ret >= sizeof(buf)) {
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l0g("session count corrupt (overflow)\n");
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* @fd: file descriptor to write to
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* @nv: new value to write
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* @filename: filename, only used for l0g()
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* Writes @nv as a number in hexadecimal to the start of the file @fd and
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* truncates the file to the written length.
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static int write_count(int fd, long nv, const char *filename) {
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char buf[ASCIIZ_LLX];
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if (unlink(filename) >= 0)
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l0g("could not unlink %s: %s\n", filename, strerror(errno));
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* Fallback to just blanking the file. This can happen when
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* pmvarrun is called as unprivileged user.
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if (ftruncate(fd, 0) < 0)
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w4rn("truncate failed: %s\n", strerror(errno));
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if ((ret = lseek(fd, 0, SEEK_SET)) != 0) {
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l0g("failed to seek in %s: %s\n", filename, strerror(errno));
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len = snprintf(buf, sizeof(buf), "0x%lX", nv);
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if ((wrt = write(fd, buf, len)) != len) {
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l0g("wrote %d of %d bytes; write error on %s: %s\n",
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(wrt < 0) ? 0 : wrt, len, filename, strerror(errno));
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if (ftruncate(fd, len) < 0) {
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l0g("truncate failed: %s\n", strerror(errno));
added
removed
.pc/hurd-path-max-define/src/pmvarrun.c
