From ba24567fd90702ea40ff320a79bc921b38510f22 Mon Sep 17 00:00:00 2001 From: Miroslav Rezanina Date: Thu, 21 Jan 2016 07:17:43 +0100 Subject: [PATCH 2/2] fw_cfg: add check to validate current entry value (CVE-2016-1714) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Miroslav Rezanina Message-id: <1453360663-5066-1-git-send-email-mrezanin@redhat.com> Patchwork-id: 68834 O-Subject: [RHEL-7.2.z/RHEL-7.3 qemu-kvm PATCH] fw_cfg: add check to validate current entry value (CVE-2016-1714) Bugzilla: 1298048 RH-Acked-by: Laurent Vivier RH-Acked-by: Laszlo Ersek RH-Acked-by: Gerd Hoffmann From: Prasad J Pandit When processing firmware configurations, an OOB r/w access occurs if 's->cur_entry' is set to be invalid(FW_CFG_INVALID=0xffff). Add a check to validate 's->cur_entry' to avoid such access. This patch is based on upstream commit 66f8fd9dda312191b78d2a2ba2848bcee76127a2 Author: Gabriel L. Somlo Date: Thu Nov 5 09:32:50 2015 -0500 fw_cfg: avoid calculating invalid current entry pointer When calculating a pointer to the currently selected fw_cfg item, the following is used: FWCfgEntry *e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK]; When s->cur_entry is FW_CFG_INVALID, we are calculating the address of a non-existent element in s->entries[arch][...], which is undefined. This patch ensures the resulting entry pointer is set to NULL whenever s->cur_entry is FW_CFG_INVALID. Reported-by: Laszlo Ersek Reviewed-by: Laszlo Ersek Signed-off-by: Gabriel Somlo Message-id: 1446733972-1602-5-git-send-email-somlo@cmu.edu Cc: Marc Marí Signed-off-by: Gabriel Somlo Reviewed-by: Laszlo Ersek Signed-off-by: Gerd Hoffmann with added chunk for fw_cfg_write() that was removed in commit 023e3148567ac898c7258138f8e86c3c2bb40d07 and missing chunk for fw_cfg_dma_transfer that was added in commit a4c0d1deb785611c96a455f65ec032976b00b36f. Reported-by: Donghai Zdh Signed-off-by: Prasad J Pandit Signed-off-by: Miroslav Rezanina --- hw/nvram/fw_cfg.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c index b865c09..fcb3146 100644 --- a/hw/nvram/fw_cfg.c +++ b/hw/nvram/fw_cfg.c @@ -207,12 +207,15 @@ static void fw_cfg_reboot(FWCfgState *s) static void fw_cfg_write(FWCfgState *s, uint8_t value) { int arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL); - FWCfgEntry *e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK]; + FWCfgEntry *e = (s->cur_entry == FW_CFG_INVALID) ? NULL : + &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK]; trace_fw_cfg_write(s, value); - if (s->cur_entry & FW_CFG_WRITE_CHANNEL && e->callback && - s->cur_offset < e->len) { + if (s->cur_entry & FW_CFG_WRITE_CHANNEL + && e != NULL + && e->callback + && s->cur_offset < e->len) { e->data[s->cur_offset++] = value; if (s->cur_offset == e->len) { e->callback(e->callback_opaque, e->data); @@ -241,7 +244,8 @@ static int fw_cfg_select(FWCfgState *s, uint16_t key) static uint8_t fw_cfg_read(FWCfgState *s) { int arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL); - FWCfgEntry *e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK]; + FWCfgEntry *e = (s->cur_entry == FW_CFG_INVALID) ? NULL : + &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK]; uint8_t ret; if (s->cur_entry == FW_CFG_INVALID || !e->data || s->cur_offset >= e->len) -- 1.8.3.1