thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

3 files changed, 360 insertions, 0 deletions

diff --git a/Documentation/sphinx-static/custom.css b/Documentation/sphinx-static/custom.css
new file mode 100644
index 000000000..6c03dca44
--- /dev/null
+++ b/Documentation/sphinx-static/custom.css
@@ -0,0 +1,203 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
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+ */
+
+div.body {  max-width: 120em; }
+
+/* Shrink the headers a bit */
+div.body h1 { font-size: 180%; }
+div.body h2 { font-size: 150%; }
+div.body h3 { font-size: 130%; }
+div.body h4 { font-size: 110%; }
+
+/* toctree captions are styled like h2 */
+div.toctree-wrapper p.caption[role=heading] { font-size: 150%; }
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+/* Tighten up the layout slightly */
+div.body { padding: 0 15px 0 10px; }
+div.sphinxsidebarwrapper { padding: 1em 0.4em; }
+div.sphinxsidebar { font-size: inherit;
+		    max-height: 100%;
+		    overflow-y: auto; }
+/* Tweak document margins and don't force width */
+div.document {
+    margin: 20px 10px 0 10px;
+    width: auto;
+}
+
+/* Size the logo appropriately */
+img.logo {
+    width: 104px;
+    margin-bottom: 20px;
+}
+
+/* The default is to use -1em, which makes it override text */
+li { text-indent: 0em; }
+
+/*
+ * Parameters for the display of function prototypes and such included
+ * from C source files.
+ */
+dl.function, dl.struct, dl.enum { margin-top: 2em; background-color: #ecf0f3; }
+/* indent lines 2+ of multi-line function prototypes */
+dl.function dt { margin-left: 10em; text-indent: -10em; }
+/*
+ * Preserve C API signatures on one line and apply contained horizontal
+ * scrolling to prevent them from exceeding their container width and
+ * breaking page layout.
+ */
+dl.c { overflow-x: auto; overflow-y: hidden; }
+dl.c > dt.sig.sig-object { white-space: nowrap; }
+dt.sig-object { font-size: larger; }
+div.kernelindent { margin-left: 2em; margin-right: 4em; }
+
+/*
+ * Parameters for the display of function prototypes and such included
+ * from Python source files.
+ */
+dl.py { margin-top: 2em; background-color: #ecf0f3; }
+dl.py.class { margin-left: 2em; text-indent: -2em; padding-left: 2em; }
+dl.py.method, dl.py.attribute { margin-left: 2em; text-indent: -2em; }
+dl.py li, pre { text-indent: 0em; padding-left: 0 !important; }
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+/*
+ * Tweaks for our local TOC
+ */
+div.kerneltoc li.toctree-l1 { font-size: smaller;
+		text-indent: -1em;
+		margin-left: 1em; }
+div.kerneltoc li.current > a {font-weight: bold; }
+div.kerneltoc li.toctree-l2,li.toctree-l3 { font-size: small;
+		text-indent: -1em;
+		margin-left: 1em;
+		list-style-type: none;
+	      }
+div.kerneltoc li.current ul { margin-left: 0; }
+div.kerneltoc { background-color: #eeeeee; }
+div.kerneltoc li.current ul { background-color: white; }
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+/*
+ * Hide toctree captions on the welcome page, they should only be shown in the
+ * sidebar.
+ */
+section#the-linux-kernel-documentation p.caption { display: none; }
+
+/*
+ * Make section titles bold in the sidebar, and decrease their bottom margin to
+ * group them with their subsections.
+ */
+div.sphinxsidebar p.caption { font-weight: bold; margin-bottom: 0; }
+div.sphinxsidebar p.caption + ul { margin-top: 0; }
+
+/*
+ * The CSS magic to toggle the contents on small screens.
+ */
+label.kernel-toc-title { display: none; }
+label.kernel-toc-title:after {
+    content: "[Hide]";
+}
+input[type=checkbox]:checked ~ label.kernel-toc-title:after {
+    content: "[Show]";
+}
+/* Hide the toggle on large screens */
+input.kernel-toc-toggle { display: none; }
+
+/*
+ * Show and implement the toggle on small screens.
+ * The 875px width seems to be wired into alabaster.
+ */
+@media screen and (max-width: 875px) {
+    label.kernel-toc-title { display: inline;
+			     font-weight: bold;
+			     font-size: larger; }
+    input[type=checkbox]:checked ~ div.kerneltoc {
+	display: none;
+    }
+    h3.kernel-toc-contents { display: inline; }
+    div.kerneltoc a { color: black; }
+}
+
+/* Language selection menu */
+
+div.admonition {
+    /*
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+}
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+    background: #eeeeee;
+    border: 1px solid #cccccc;
+    margin-bottom: 1em;
+    padding: .5em;
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+    position: relative;
+    float: right;
+}
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+div.language-selection a {
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+    color: #333333;
+    text-decoration: none;
+}
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+    position: absolute;
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+    /* Align with the parent div */
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+    right: 0;
+    margin: 0;
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+    list-style: none;
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+    background: #fafafa;
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+    /* Never break menu item lines */
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+}
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+div.language-selection:hover ul {
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+}
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+div.language-selection ul li:hover {
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+}
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+/* Let rendered reference links in tables wrap when needed. */
+div.body table.docutils a.reference {
+    overflow-wrap: anywhere;
+}
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+}
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+/* Make xrefs more universally visible */
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+}
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+/* Slightly different style for sidebar links */
+div.sphinxsidebar a { border-bottom: none; }
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diff --git a/Documentation/sphinx-static/theme_overrides.css b/Documentation/sphinx-static/theme_overrides.css
new file mode 100644
index 000000000..79000b26e
--- /dev/null
+++ b/Documentation/sphinx-static/theme_overrides.css
@@ -0,0 +1,120 @@
+/* -*- coding: utf-8; mode: css -*-
+ *
+ * Sphinx HTML theme customization: read the doc
+ * Please don't add any color definition here, as the theme should
+ * work for both normal and dark modes.
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+/* Improve contrast and increase size for easier reading. */
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+	font-family: serif;
+	font-size: 100%;
+}
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+}
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+	font-size: 100%;
+}
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+}
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+}
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+}
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+}
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+}
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+@media screen {
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+    /* content column
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+    .wy-nav-content{max-width: none; }
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+    /* table:
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+     *   - align caption "left" ("center" is unsuitable on vast tables)
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+    .rst-content table.docutils caption { text-align: left; font-size: 100%; }
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+    /* captions:
+     *
+     *   - captions should have 100% (not 85%) font size
+     *   - hide the permalink symbol as long as link is not hovered
+     */
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+    caption, .wy-table caption, .rst-content table.field-list caption {
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+    caption a.headerlink { opacity: 0; }
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+
+    /* fix bottom margin of lists items */
+
+    .rst-content .section ul li:last-child, .rst-content .section ul li p:last-child {
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+    }
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+    /* inline literal: drop the borderbox, padding and red color */
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diff --git a/Documentation/sphinx-static/theme_rtd_colors.css b/Documentation/sphinx-static/theme_rtd_colors.css
new file mode 100644
index 000000000..55b6e1c36
--- /dev/null
+++ b/Documentation/sphinx-static/theme_rtd_colors.css
@@ -0,0 +1,37 @@
+/* -*- coding: utf-8; mode: css -*-
+ *
+ * Sphinx HTML theme customization: color settings for RTD (non-dark) theme
+ *
+ */
+
+/* Improve contrast and increase size for easier reading. */
+
+body {
+	color: black;
+}
+
+.wy-menu-vertical li.current a {
+	color: #505050;
+}
+
+.wy-menu-vertical li.on a, .wy-menu-vertical li.current > a {
+	color: #303030;
+}
+
+div[class^="highlight"] pre {
+	color: black;
+}
+
+@media screen {
+
+    /* Menu selection and keystrokes */
+
+    span.menuselection {
+	color: blue;
+    }
+
+    code.kbd, code.kbd span {
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+	background-color: darkblue;
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+}