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From 66f8fd9dda312191b78d2a2ba2848bcee76127a2 Mon Sep 17 00:00:00 2001
From: "Gabriel L. Somlo" <somlo@cmu.edu>
Date: Thu, 5 Nov 2015 09:32:50 -0500
Subject: [PATCH] fw_cfg: avoid calculating invalid current entry pointer
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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 <lersek@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
Message-id: 1446733972-1602-5-git-send-email-somlo@cmu.edu
Cc: Marc Marí <markmb@redhat.com>
Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
hw/nvram/fw_cfg.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index c2d3a0a..046fa74 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -277,7 +277,8 @@ 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)
@@ -342,7 +343,8 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
}
arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL);
- e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
+ e = (s->cur_entry == FW_CFG_INVALID) ? NULL :
+ &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
if (dma.control & FW_CFG_DMA_CTL_READ) {
read = 1;
--
2.7.4
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