59 lines
2.0 KiB
Diff
59 lines
2.0 KiB
Diff
From 153c8db09b26455aa9802ff95943dd8a75f31893 Mon Sep 17 00:00:00 2001
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From: Gary Lockyer <gary@catalyst.net.nz>
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Date: Wed, 24 Jun 2020 14:27:08 +1200
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Subject: [PATCH 20/22] CVE-2020-14303: s4 nbt: fix busy loop on empty UDP
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packet
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An empty UDP packet put the nbt server into a busy loop that consumes
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100% of a cpu.
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BUG: https://bugzilla.samba.org/show_bug.cgi?id=14417
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Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
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---
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libcli/nbt/nbtsocket.c | 17 ++++++++++++++++-
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selftest/knownfail.d/empty-nbt | 1 -
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2 files changed, 16 insertions(+), 2 deletions(-)
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delete mode 100644 selftest/knownfail.d/empty-nbt
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diff --git a/libcli/nbt/nbtsocket.c b/libcli/nbt/nbtsocket.c
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index 33d53fba993..8aecaf73247 100644
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--- a/libcli/nbt/nbtsocket.c
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+++ b/libcli/nbt/nbtsocket.c
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@@ -167,8 +167,23 @@ static void nbt_name_socket_recv(struct nbt_name_socket *nbtsock)
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return;
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}
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+ /*
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+ * Given a zero length, data_blob_talloc() returns the
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+ * NULL blob {NULL, 0}.
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+ *
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+ * We only want to error return here on a real out of memory condition
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+ * (i.e. dsize != 0, so the UDP packet has data, but the return of the
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+ * allocation failed, so blob.data==NULL).
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+ *
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+ * Given an actual zero length UDP packet having blob.data == NULL
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+ * isn't an out of memory error condition, that's the defined semantics
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+ * of data_blob_talloc() when asked for zero bytes.
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+ *
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+ * We still need to continue to do the zero-length socket_recvfrom()
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+ * read in order to clear the "read pending" condition on the socket.
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+ */
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blob = data_blob_talloc(tmp_ctx, NULL, dsize);
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- if (blob.data == NULL) {
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+ if (blob.data == NULL && dsize != 0) {
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talloc_free(tmp_ctx);
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return;
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}
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diff --git a/selftest/knownfail.d/empty-nbt b/selftest/knownfail.d/empty-nbt
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deleted file mode 100644
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index e4bcccab4e5..00000000000
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--- a/selftest/knownfail.d/empty-nbt
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+++ /dev/null
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@@ -1 +0,0 @@
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-^samba.tests.dns_packet.samba.tests.dns_packet.TestNbtPackets.test_empty_packet
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\ No newline at end of file
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--
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2.17.1
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