forked from rpms/glibc
205 lines
5.8 KiB
Diff
205 lines
5.8 KiB
Diff
commit 628598be7e1bfaa04f34df71ef6678f2c5103dfd
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Thu Aug 15 16:09:05 2019 +0200
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login: Disarm timer after utmp lock acquisition [BZ #24879]
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If the file processing takes a long time for some reason, SIGALRM can
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arrive while the file is still being processed. At that point, file
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access will fail with EINTR. Disarming the timer after lock
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acquisition avoids that. (If there was a previous alarm, it is the
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responsibility of the caller to deal with the EINTR error.)
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diff --git a/login/utmp_file.c b/login/utmp_file.c
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index 8b6fee96b623fa90..a736d3d25e005920 100644
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--- a/login/utmp_file.c
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+++ b/login/utmp_file.c
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@@ -55,32 +55,23 @@ static void timeout_handler (int signum) {};
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/* try_file_lock (LOCKING, FD, TYPE) returns true if the locking
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operation failed and recovery needs to be performed.
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- (file_lock_restore (LOCKING) still needs to be called.)
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file_unlock (FD) removes the lock (which must have been
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- acquired).
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-
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- file_lock_restore (LOCKING) is needed to clean up in both
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- cases. */
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-
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-struct file_locking
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-{
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- struct sigaction old_action;
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- unsigned int old_timeout;
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-};
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+ successfully acquired). */
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static bool
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-try_file_lock (struct file_locking *locking, int fd, int type)
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+try_file_lock (int fd, int type)
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{
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/* Cancel any existing alarm. */
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- locking->old_timeout = alarm (0);
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+ int old_timeout = alarm (0);
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/* Establish signal handler. */
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+ struct sigaction old_action;
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struct sigaction action;
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action.sa_handler = timeout_handler;
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__sigemptyset (&action.sa_mask);
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action.sa_flags = 0;
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- __sigaction (SIGALRM, &action, &locking->old_action);
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+ __sigaction (SIGALRM, &action, &old_action);
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alarm (TIMEOUT);
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@@ -90,7 +81,23 @@ try_file_lock (struct file_locking *locking, int fd, int type)
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.l_type = type,
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fl.l_whence = SEEK_SET,
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};
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- return __fcntl64_nocancel (fd, F_SETLKW, &fl) < 0;
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+
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+ bool status = __fcntl64_nocancel (fd, F_SETLKW, &fl) < 0;
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+ int saved_errno = errno;
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+
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+ /* Reset the signal handler and alarm. We must reset the alarm
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+ before resetting the handler so our alarm does not generate a
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+ spurious SIGALRM seen by the user. However, we cannot just set
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+ the user's old alarm before restoring the handler, because then
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+ it's possible our handler could catch the user alarm's SIGARLM and
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+ then the user would never see the signal he expected. */
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+ alarm (0);
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+ __sigaction (SIGALRM, &old_action, NULL);
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+ if (old_timeout != 0)
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+ alarm (old_timeout);
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+
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+ __set_errno (saved_errno);
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+ return status;
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}
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static void
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@@ -103,21 +110,6 @@ file_unlock (int fd)
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__fcntl64_nocancel (fd, F_SETLKW, &fl);
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}
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-static void
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-file_lock_restore (struct file_locking *locking)
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-{
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- /* Reset the signal handler and alarm. We must reset the alarm
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- before resetting the handler so our alarm does not generate a
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- spurious SIGALRM seen by the user. However, we cannot just set
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- the user's old alarm before restoring the handler, because then
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- it's possible our handler could catch the user alarm's SIGARLM
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- and then the user would never see the signal he expected. */
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- alarm (0);
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- __sigaction (SIGALRM, &locking->old_action, NULL);
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- if (locking->old_timeout != 0)
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- alarm (locking->old_timeout);
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-}
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-
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#ifndef TRANSFORM_UTMP_FILE_NAME
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# define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
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#endif
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@@ -166,8 +158,7 @@ __libc_getutent_r (struct utmp *buffer, struct utmp **result)
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return -1;
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}
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- struct file_locking fl;
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- if (try_file_lock (&fl, file_fd, F_RDLCK))
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+ if (try_file_lock (file_fd, F_RDLCK))
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nbytes = 0;
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else
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{
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@@ -175,7 +166,6 @@ __libc_getutent_r (struct utmp *buffer, struct utmp **result)
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nbytes = __read_nocancel (file_fd, &last_entry, sizeof (struct utmp));
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file_unlock (file_fd);
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}
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- file_lock_restore (&fl);
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if (nbytes != sizeof (struct utmp))
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{
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@@ -201,11 +191,9 @@ internal_getut_r (const struct utmp *id, struct utmp *buffer,
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{
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int result = -1;
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- struct file_locking fl;
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- if (try_file_lock (&fl, file_fd, F_RDLCK))
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+ if (try_file_lock (file_fd, F_RDLCK))
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{
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*lock_failed = true;
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- file_lock_restore (&fl);
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return -1;
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}
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@@ -257,7 +245,6 @@ internal_getut_r (const struct utmp *id, struct utmp *buffer,
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unlock_return:
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file_unlock (file_fd);
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- file_lock_restore (&fl);
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return result;
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}
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@@ -303,11 +290,9 @@ __libc_getutline_r (const struct utmp *line, struct utmp *buffer,
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return -1;
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}
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- struct file_locking fl;
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- if (try_file_lock (&fl, file_fd, F_RDLCK))
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+ if (try_file_lock (file_fd, F_RDLCK))
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{
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*result = NULL;
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- file_lock_restore (&fl);
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return -1;
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}
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@@ -337,7 +322,6 @@ __libc_getutline_r (const struct utmp *line, struct utmp *buffer,
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unlock_return:
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file_unlock (file_fd);
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- file_lock_restore (&fl);
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return ((*result == NULL) ? -1 : 0);
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}
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@@ -394,12 +378,8 @@ __libc_pututline (const struct utmp *data)
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}
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}
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- struct file_locking fl;
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- if (try_file_lock (&fl, file_fd, F_WRLCK))
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- {
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- file_lock_restore (&fl);
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- return NULL;
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- }
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+ if (try_file_lock (file_fd, F_WRLCK))
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+ return NULL;
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if (found < 0)
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{
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@@ -442,7 +422,6 @@ __libc_pututline (const struct utmp *data)
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unlock_return:
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file_unlock (file_fd);
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- file_lock_restore (&fl);
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return pbuf;
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}
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@@ -471,10 +450,8 @@ __libc_updwtmp (const char *file, const struct utmp *utmp)
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if (fd < 0)
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return -1;
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- struct file_locking fl;
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- if (try_file_lock (&fl, fd, F_WRLCK))
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+ if (try_file_lock (fd, F_WRLCK))
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{
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- file_lock_restore (&fl);
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__close_nocancel_nostatus (fd);
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return -1;
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}
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@@ -504,7 +481,6 @@ __libc_updwtmp (const char *file, const struct utmp *utmp)
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unlock_return:
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file_unlock (fd);
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- file_lock_restore (&fl);
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/* Close WTMP file. */
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__close_nocancel_nostatus (fd);
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