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From 5d12c17191e042a57e02749cedc55104a8251ac3 Mon Sep 17 00:00:00 2001
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From: Miroslav Rezanina <mrezanin@redhat.com>
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Date: Thu, 21 Jan 2016 07:17:43 +0100
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Subject: [PATCH] fw_cfg: add check to validate current entry value
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(CVE-2016-1714)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Message-id: <1453360663-5066-1-git-send-email-mrezanin@redhat.com>
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Patchwork-id: 68834
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O-Subject: [RHEL-7.2.z/RHEL-7.3 qemu-kvm PATCH] fw_cfg: add check to validate current entry value (CVE-2016-1714)
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Bugzilla: 1298047
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>
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From: Prasad J Pandit <pjp@fedoraproject.org>
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When processing firmware configurations, an OOB r/w access occurs
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if 's->cur_entry' is set to be invalid(FW_CFG_INVALID=0xffff).
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Add a check to validate 's->cur_entry' to avoid such access.
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This patch is based on upstream commit 66f8fd9dda312191b78d2a2ba2848bcee76127a2
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Author: Gabriel L. Somlo <somlo@cmu.edu>
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Date: Thu Nov 5 09:32:50 2015 -0500
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fw_cfg: avoid calculating invalid current entry pointer
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When calculating a pointer to the currently selected fw_cfg item, the
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following is used:
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FWCfgEntry *e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
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When s->cur_entry is FW_CFG_INVALID, we are calculating the address of
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a non-existent element in s->entries[arch][...], which is undefined.
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This patch ensures the resulting entry pointer is set to NULL whenever
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s->cur_entry is FW_CFG_INVALID.
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Reported-by: Laszlo Ersek <lersek@redhat.com>
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Reviewed-by: Laszlo Ersek <lersek@redhat.com>
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Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
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Message-id: 1446733972-1602-5-git-send-email-somlo@cmu.edu
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Cc: Marc Marí <markmb@redhat.com>
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Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
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Reviewed-by: Laszlo Ersek <lersek@redhat.com>
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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with added chunk for fw_cfg_write() that was removed in commit
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023e3148567ac898c7258138f8e86c3c2bb40d07
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and missing chunk for fw_cfg_dma_transfer that was added in commit
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a4c0d1deb785611c96a455f65ec032976b00b36f.
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Reported-by: Donghai Zdh <donghai.zdh@alibaba-inc.com>
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Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/nvram/fw_cfg.c | 12 ++++++++----
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1 file changed, 8 insertions(+), 4 deletions(-)
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diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
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index b865c09..fcb3146 100644
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--- a/hw/nvram/fw_cfg.c
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+++ b/hw/nvram/fw_cfg.c
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@@ -207,12 +207,15 @@ static void fw_cfg_reboot(FWCfgState *s)
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static void fw_cfg_write(FWCfgState *s, uint8_t value)
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{
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int arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL);
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- FWCfgEntry *e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
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+ FWCfgEntry *e = (s->cur_entry == FW_CFG_INVALID) ? NULL :
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+ &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
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trace_fw_cfg_write(s, value);
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- if (s->cur_entry & FW_CFG_WRITE_CHANNEL && e->callback &&
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- s->cur_offset < e->len) {
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+ if (s->cur_entry & FW_CFG_WRITE_CHANNEL
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+ && e != NULL
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+ && e->callback
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+ && s->cur_offset < e->len) {
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e->data[s->cur_offset++] = value;
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if (s->cur_offset == e->len) {
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e->callback(e->callback_opaque, e->data);
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@@ -241,7 +244,8 @@ static int fw_cfg_select(FWCfgState *s, uint16_t key)
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static uint8_t fw_cfg_read(FWCfgState *s)
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{
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int arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL);
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- FWCfgEntry *e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
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+ FWCfgEntry *e = (s->cur_entry == FW_CFG_INVALID) ? NULL :
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+ &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
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uint8_t ret;
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if (s->cur_entry == FW_CFG_INVALID || !e->data || s->cur_offset >= e->len)
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--
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1.8.3.1
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