From 6fc12b327982851378333d24fc902c3540dadc0e Mon Sep 17 00:00:00 2001
From: Michal Sekletar <msekleta@redhat.com>
Date: Tue, 20 Feb 2018 14:16:15 +0100
Subject: [PATCH] sd-journal: when picking up a new file, compare inode/device
 info with previous open file by same name

Let's make sure we aren't confused if a journal file is replaced by a
different one (for example due to rotation) if we are in a q overflow:
let's compare the inode/device information, and if it changed replace
any open file object as needed.

Fixes: #8198

(cherry-picked from commit 32cb1983ad6f7084ff86e259ff079742a8139719)

[msekleta: this is very slimmed down version of the above commit because
a lot of code from is not applicable to RHEL-7 version]

Related: #1540538
---
 src/journal/sd-journal.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index e1cde6e1c..004fe646d 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -1224,20 +1224,43 @@ static bool file_type_wanted(int flags, const char *filename) {
 
 static int add_any_file(sd_journal *j, const char *path) {
         JournalFile *f = NULL;
+        struct stat st;
         int r, k;
 
         assert(j);
         assert(path);
 
-        if (path) {
-                f = ordered_hashmap_get(j->files, path);
-                if (f) {
-                        /* Mark this file as seen in this generation. This is used to GC old files in
-                         * process_q_overflow() to detect journal files that are still and discern them from those who
-                         * are gone. */
+        if (stat(path, &st) < 0) {
+                r = log_debug_errno(errno, "Failed to stat file '%s': %m", path);
+                return -errno;
+        }
+        if (S_ISDIR(st.st_mode)) {
+                log_debug("Uh, file '%s' is a directory? Refusing.", path);
+                return -EISDIR;
+        }
+        if (!S_ISREG(st.st_mode)) {
+                log_debug("Uh, file '%s' is not a regular file? Refusing.", path);
+                return -EBADFD;
+        }
+
+        f = ordered_hashmap_get(j->files, path);
+        if (f) {
+
+                if (f->last_stat.st_dev == st.st_dev &&
+                    f->last_stat.st_ino == st.st_ino) {
+
+                        /* We already track this file, under the same path and with the same device/inode numbers, it's hence
+                         * really the same. Mark this file as seen in this generation. This is used to GC old files in
+                         * process_q_overflow() to detect journal files that are still and discern them from those who are
+                         * gone. */
                         f->last_seen_generation = j->generation;
                         return 0;
                 }
+
+                /* So we tracked a file under this name, but it has a different inode/device. In that case, it got
+                 * replaced (probably due to rotation?), let's drop it hence from our list. */
+                remove_file_real(j, f);
+                f = NULL;
         }
 
         if (ordered_hashmap_size(j->files) >= JOURNAL_FILES_MAX) {