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From b173eba1698138f92b08d4deeaac4d2979a67bbf Mon Sep 17 00:00:00 2001
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From: Frediano Ziglio <freddy77@gmail.com>
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Date: Fri, 2 Oct 2020 12:27:59 +0100
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Subject: [PATCH vd_agent_linux 11/17] Avoids uncontrolled "active_xfers"
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allocations
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Limit the number of active file transfers possibly causing DoSes
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consuming memory in "active_xfers".
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This issue was reported by SUSE security team.
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Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
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Acked-by: Uri Lublin <uril@redhat.com>
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---
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src/vdagentd/vdagentd.c | 23 +++++++++++++++++++++++
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1 file changed, 23 insertions(+)
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diff --git a/src/vdagentd/vdagentd.c b/src/vdagentd/vdagentd.c
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index 8961a99..b31941d 100644
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--- a/src/vdagentd/vdagentd.c
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+++ b/src/vdagentd/vdagentd.c
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@@ -47,6 +47,14 @@
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#define DEFAULT_UINPUT_DEVICE "/dev/uinput"
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+// Maximum number of transfers active at any time.
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+// Avoid DoS from client.
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+// As each transfer could likely end up taking a file descriptor
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+// it is good to have a limit less than the number of file descriptors
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+// in the process (by default 1024). The daemon do not open file
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+// descriptors for the transfers but the agents do.
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+#define MAX_ACTIVE_TRANSFERS 128
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+
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struct agent_data {
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char *session;
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int width;
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@@ -380,6 +388,21 @@ static void do_client_file_xfer(VirtioPort *vport,
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"Cancelling client file-xfer request %u",
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s->id, VD_AGENT_FILE_XFER_STATUS_SESSION_LOCKED, NULL, 0);
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return;
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+ } else if (g_hash_table_size(active_xfers) >= MAX_ACTIVE_TRANSFERS) {
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+ VDAgentFileXferStatusError error = {
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+ GUINT32_TO_LE(VD_AGENT_FILE_XFER_STATUS_ERROR_GLIB_IO),
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+ GUINT32_TO_LE(G_IO_ERROR_TOO_MANY_OPEN_FILES),
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+ };
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+ size_t detail_size = sizeof(error);
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+ if (!VD_AGENT_HAS_CAPABILITY(capabilities, capabilities_size,
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+ VD_AGENT_CAP_FILE_XFER_DETAILED_ERRORS)) {
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+ detail_size = 0;
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+ }
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+ send_file_xfer_status(vport,
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+ "Too many transfers ongoing. "
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+ "Cancelling client file-xfer request %u",
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+ s->id, VD_AGENT_FILE_XFER_STATUS_ERROR, (void*) &error, detail_size);
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+ return;
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}
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msg_type = VDAGENTD_FILE_XFER_START;
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id = s->id;
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--
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2.26.2
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