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From 94809b687fbb1c43b07ed8aa966070079cdcb063 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
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Date: Thu, 3 Jan 2019 16:09:05 +0100
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Subject: [PATCH] journald: set a limit on the number of fields (1k)
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We allocate a iovec entry for each field, so with many short entries,
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our memory usage and processing time can be large, even with a relatively
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small message size. Let's refuse overly long entries.
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CVE-2018-16865
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https://bugzilla.redhat.com/show_bug.cgi?id=1653861
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What from I can see, the problem is not from an alloca, despite what the CVE
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description says, but from the attack multiplication that comes from creating
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many very small iovecs: (void* + size_t) for each three bytes of input
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message.
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Resolves: #1657792
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---
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src/journal/journal-file.h | 3 +++
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src/journal/journald-native.c | 4 ++++
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2 files changed, 7 insertions(+)
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diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h
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index dd8ef52d2..37749c445 100644
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--- a/src/journal/journal-file.h
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+++ b/src/journal/journal-file.h
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@@ -158,6 +158,9 @@ int journal_file_open_reliably(
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* files without adding too many zeros. */
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#define OFSfmt "%06"PRIx64
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+/* The maximum number of fields in an entry */
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+#define ENTRY_FIELD_COUNT_MAX 1024
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+
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static inline bool VALID_REALTIME(uint64_t u) {
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/* This considers timestamps until the year 3112 valid. That should be plenty room... */
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return u > 0 && u < (1ULL << 55);
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diff --git a/src/journal/journald-native.c b/src/journal/journald-native.c
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index cf3349393..0c451274f 100644
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--- a/src/journal/journald-native.c
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+++ b/src/journal/journald-native.c
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@@ -134,6 +134,10 @@ void server_process_native_message(
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}
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/* A property follows */
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+ if (n > ENTRY_FIELD_COUNT_MAX) {
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+ log_debug("Received an entry that has more than " STRINGIFY(ENTRY_FIELD_COUNT_MAX) " fields, ignoring entry.");
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+ goto finish;
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+ }
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/* n existing properties, 1 new, +1 for _TRANSPORT */
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if (!GREEDY_REALLOC(iovec, m, n + 2 + N_IOVEC_META_FIELDS + N_IOVEC_OBJECT_FIELDS)) {
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