82 lines
2.8 KiB
Diff
82 lines
2.8 KiB
Diff
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From 88d7c7c51b4523add8b7d48209b5b6a316442e0f Mon Sep 17 00:00:00 2001
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From: Phil Sutter <phil@nwl.cc>
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Date: Thu, 12 Oct 2023 17:27:42 +0200
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Subject: [PATCH] libiptc: Fix for another segfault due to chain index NULL
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pointer
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Chain rename code missed to adjust the num_chains value which is used to
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calculate the number of chain index buckets to allocate during an index
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rebuild. So with the right number of chains present, the last chain in a
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middle bucket being renamed (and ending up in another bucket) triggers
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an index rebuild based on false data. The resulting NULL pointer index
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bucket then causes a segfault upon reinsertion.
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Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1713
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Fixes: 64ff47cde38e4 ("libiptc: fix chain rename bug in libiptc")
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(cherry picked from commit e2d7ee9c49b582f399ad4ba2da2ee1b3e1f89620)
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---
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.../testcases/chain/0008rename-segfault2_0 | 32 +++++++++++++++++++
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libiptc/libiptc.c | 4 +++
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2 files changed, 36 insertions(+)
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create mode 100755 iptables/tests/shell/testcases/chain/0008rename-segfault2_0
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diff --git a/iptables/tests/shell/testcases/chain/0008rename-segfault2_0 b/iptables/tests/shell/testcases/chain/0008rename-segfault2_0
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new file mode 100755
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index 0000000000000..bc473d2511bbd
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--- /dev/null
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+++ b/iptables/tests/shell/testcases/chain/0008rename-segfault2_0
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@@ -0,0 +1,32 @@
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+#!/bin/bash
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+#
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+# Another funny rename bug in libiptc:
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+# If there is a chain index bucket with only a single chain in it and it is not
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+# the last one and that chain is renamed, a chain index rebuild is triggered.
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+# Since TC_RENAME_CHAIN missed to temporarily decrement num_chains value, an
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+# extra index is allocated and remains NULL. The following insert of renamed
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+# chain then segfaults.
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+
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+(
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+ echo "*filter"
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+ # first bucket
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+ for ((i = 0; i < 40; i++)); do
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+ echo ":chain-a-$i - [0:0]"
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+ done
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+ # second bucket
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+ for ((i = 0; i < 40; i++)); do
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+ echo ":chain-b-$i - [0:0]"
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+ done
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+ # third bucket, just make sure it exists
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+ echo ":chain-c-0 - [0:0]"
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+ echo "COMMIT"
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+) | $XT_MULTI iptables-restore
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+
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+# rename all chains of the middle bucket
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+(
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+ echo "*filter"
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+ for ((i = 0; i < 40; i++)); do
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+ echo "-E chain-b-$i chain-d-$i"
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+ done
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+ echo "COMMIT"
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+) | $XT_MULTI iptables-restore --noflush
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diff --git a/libiptc/libiptc.c b/libiptc/libiptc.c
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index e475063367c26..9712a36353b9a 100644
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--- a/libiptc/libiptc.c
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+++ b/libiptc/libiptc.c
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@@ -2384,12 +2384,16 @@ int TC_RENAME_CHAIN(const IPT_CHAINLABEL oldname,
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return 0;
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}
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+ handle->num_chains--;
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+
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/* This only unlinks "c" from the list, thus no free(c) */
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iptcc_chain_index_delete_chain(c, handle);
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/* Change the name of the chain */
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strncpy(c->name, newname, sizeof(IPT_CHAINLABEL) - 1);
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+ handle->num_chains++;
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+
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/* Insert sorted into to list again */
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iptc_insert_chain(handle, c);
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