From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Wed, 15 Dec 2021 17:18:25 +0000 (+0100)
Subject: journal: Correctly advance offset when iterating hash table entries
X-Git-Tag: v250-rc3~40^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cdbba4487811bb14714ba462713298b2bda719c7;p=thirdparty%2Fsystemd.git

journal: Correctly advance offset when iterating hash table entries

pread() is not guaranteed to completely fill up the given buffer with
data which we assumed until now. Instead, only increment the offset by
the number of bytes that were actually read.
---

diff --git a/src/journal/journald-file.c b/src/journal/journald-file.c
index 78580ca84d6..bf0933189cc 100644
--- a/src/journal/journald-file.c
+++ b/src/journal/journald-file.c
@@ -81,6 +81,7 @@ static int journald_file_punch_holes(JournalFile *f) {
         HashItem items[4096 / sizeof(HashItem)];
         uint64_t p, sz;
         size_t to_read;
+        ssize_t n;
         int r;
 
         r = journald_file_entry_array_punch_hole(
@@ -92,14 +93,12 @@ static int journald_file_punch_holes(JournalFile *f) {
         sz = le64toh(f->header->data_hash_table_size);
         to_read = MIN((size_t) f->last_stat.st_blksize, sizeof(items));
 
-        for (uint64_t i = p; i < p + sz; i += sizeof(items)) {
-                ssize_t n_read;
+        for (uint64_t i = p; i < p + sz; i += n) {
+                n = pread(f->fd, items, MIN(to_read, p + sz - i), i);
+                if (n < 0)
+                        return n;
 
-                n_read = pread(f->fd, items, MIN(to_read, p + sz - i), i);
-                if (n_read < 0)
-                        return n_read;
-
-                for (size_t j = 0; j < (size_t) n_read / sizeof(HashItem); j++) {
+                for (size_t j = 0; j < (size_t) n / sizeof(HashItem); j++) {
                         Object o;
 
                         for (uint64_t q = le64toh(items[j].head_hash_offset); q != 0;