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commit 76a7c103eb9060f9e3ba01d073ae4621a17d8b46
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Tue Nov 12 12:02:57 2019 +0100
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login: Introduce matches_last_entry to utmp processing
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This simplifies internal_getut_nolock and fixes a regression,
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introduced in commit be6b16d975683e6cca57852cd4cfe715b2a9d8b1
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("login: Acquire write lock early in pututline [BZ #24882]")
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in pututxline because __utmp_equal can only compare process-related
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utmp entries.
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Fixes: be6b16d975683e6cca57852cd4cfe715b2a9d8b1
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Change-Id: Ib8a85002f7f87ee41590846d16d7e52bdb82f5a5
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diff --git a/login/utmp_file.c b/login/utmp_file.c
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index 6bba120db9cc574e..e653d14967c4fb7a 100644
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--- a/login/utmp_file.c
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+++ b/login/utmp_file.c
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@@ -43,6 +43,25 @@ static off64_t file_offset;
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/* Cache for the last read entry. */
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static struct utmp last_entry;
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+/* Returns true if *ENTRY matches last_entry, based on
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+ data->ut_type. */
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+static bool
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+matches_last_entry (const struct utmp *data)
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+{
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+ if (file_offset <= 0)
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+ /* Nothing has been read. last_entry is stale and cannot match. */
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+ return false;
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+
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+ if (data->ut_type == RUN_LVL
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+ || data->ut_type == BOOT_TIME
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+ || data->ut_type == OLD_TIME
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+ || data->ut_type == NEW_TIME)
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+ /* For some entry types, only a type match is required. */
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+ return data->ut_type == last_entry.ut_type;
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+ else
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+ /* For the process-related entries, a full match is needed. */
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+ return __utmp_equal (&last_entry, data);
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+}
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/* Locking timeout. */
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#ifndef TIMEOUT
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@@ -133,9 +152,6 @@ __libc_setutent (void)
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__lseek64 (file_fd, 0, SEEK_SET);
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file_offset = 0;
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- /* Make sure the entry won't match. */
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- last_entry.ut_type = -1;
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-
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return 1;
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}
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@@ -191,48 +207,20 @@ __libc_getutent_r (struct utmp *buffer, struct utmp **result)
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static int
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internal_getut_nolock (const struct utmp *id)
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{
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- if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
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- || id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
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+ while (1)
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{
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- /* Search for next entry with type RUN_LVL, BOOT_TIME,
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- OLD_TIME, or NEW_TIME. */
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-
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- while (1)
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+ /* Read the next entry. */
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+ if (__read_nocancel (file_fd, &last_entry, sizeof (struct utmp))
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+ != sizeof (struct utmp))
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{
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- /* Read the next entry. */
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- if (__read_nocancel (file_fd, &last_entry, sizeof (struct utmp))
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- != sizeof (struct utmp))
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- {
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- __set_errno (ESRCH);
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- file_offset = -1l;
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- return -1;
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- }
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- file_offset += sizeof (struct utmp);
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-
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- if (id->ut_type == last_entry.ut_type)
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- break;
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+ __set_errno (ESRCH);
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+ file_offset = -1l;
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+ return -1;
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}
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- }
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- else
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- {
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- /* Search for the next entry with the specified ID and with type
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- INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS. */
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-
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- while (1)
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- {
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- /* Read the next entry. */
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- if (__read_nocancel (file_fd, &last_entry, sizeof (struct utmp))
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- != sizeof (struct utmp))
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- {
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- __set_errno (ESRCH);
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- file_offset = -1l;
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- return -1;
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- }
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- file_offset += sizeof (struct utmp);
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+ file_offset += sizeof (struct utmp);
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- if (__utmp_equal (&last_entry, id))
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- break;
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- }
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+ if (matches_last_entry (id))
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+ break;
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}
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return 0;
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@@ -365,13 +353,7 @@ __libc_pututline (const struct utmp *data)
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/* Find the correct place to insert the data. */
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bool found = false;
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- if (file_offset > 0
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- && ((last_entry.ut_type == data->ut_type
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- && (last_entry.ut_type == RUN_LVL
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- || last_entry.ut_type == BOOT_TIME
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- || last_entry.ut_type == OLD_TIME
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- || last_entry.ut_type == NEW_TIME))
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- || __utmp_equal (&last_entry, data)))
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+ if (matches_last_entry (data))
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{
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if (__lseek64 (file_fd, file_offset, SEEK_SET) < 0)
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{
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@@ -389,7 +371,7 @@ __libc_pututline (const struct utmp *data)
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found = false;
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}
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else
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- found = __utmp_equal (&last_entry, data);
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+ found = matches_last_entry (data);
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}
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if (!found)
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