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From 9f53d3cded6cf7eccb40c810dfb8fd6e101c7a3b 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: Wed, 5 Dec 2018 22:45:02 +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 message.
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(cherry-picked from commit 052c57f132f04a3cf4148f87561618da1a6908b4)
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Resolves: #1664977
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---
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src/journal/journal-file.h | 3 +++
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src/journal/journald-native.c | 5 +++++
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2 files changed, 8 insertions(+)
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diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h
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index c8114ee2d0..cd8a48a364 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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@@ -165,6 +165,9 @@ 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 5ff22a10af..951d092053 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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@@ -140,6 +140,11 @@ static int server_process_entry(
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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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+ r = 1;
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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,
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