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Blame SOURCES/kvm-fw_cfg-avoid-calculating-invalid-current-entry-point.patch

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From 8fb3ac70845fbe261407e7782d3e6233e368da8f Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
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Date: Wed, 13 Dec 2017 13:38:37 +0100
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Subject: [PATCH 06/41] fw_cfg: avoid calculating invalid current entry pointer
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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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RH-Author: Marc-André Lureau <marcandre.lureau@redhat.com>
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Message-id: <20171213133912.26176-7-marcandre.lureau@redhat.com>
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Patchwork-id: 78355
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O-Subject: [RHEL-7.5 qemu-kvm PATCH v3 06/41] fw_cfg: avoid calculating invalid current entry pointer
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Bugzilla: 1411490
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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From: "Gabriel L. Somlo" <somlo@cmu.edu>
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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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(cherry picked from commit 66f8fd9dda312191b78d2a2ba2848bcee76127a2)
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RHEL: fix minor conflicts due to previous partial backport in commit
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      ba24567fd90702ea40ff320a79bc921b38510f22.
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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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 | 3 ++-
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 1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
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index 85e950c..1317df7 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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@@ -301,7 +301,8 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
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     }
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     arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL);
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-    e = &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
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+    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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     if (dma.control & FW_CFG_DMA_CTL_READ) {
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         read = 1;
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-- 
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1.8.3.1
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