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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/186839">186839</a></dd>
<dt>Author</dt> <dd>mcatanzaro@igalia.com</dd>
<dt>Date</dt> <dd>2015-07-15 09:01:32 -0700 (Wed, 15 Jul 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>[Linux] SeccompBrokerClient should cache arbitrary file descriptors
https://bugs.webkit.org/show_bug.cgi?id=140068
Reviewed by Žan Doberšek.
If malloc() attempts to open /proc/sys/vm/overcommit_memory in a SIGSYS
signal handler, the SeccompBroker will attempt to recursively broker the
open() syscall. Generalize the existing code that already handles the
similar case where malloc() opens /sys/devices/system/cpu/online to
handle this situation as well.
* Shared/linux/SeccompFilters/SeccompBroker.cpp:
(WebKit::SIGSYSHandler):
(WebKit::SeccompBrokerClient::SeccompBrokerClient):
(WebKit::SeccompBrokerClient::~SeccompBrokerClient):
(WebKit::SeccompBrokerClient::handleIfOpeningCachedFile):
(WebKit::SeccompBrokerClient::cacheFile):
(WebKit::SeccompBrokerClient::handleIfOpeningOnlineCPUCount): Deleted.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebKit2ChangeLog">trunk/Source/WebKit2/ChangeLog</a></li>
<li><a href="#trunkSourceWebKit2SharedlinuxSeccompFiltersSeccompBrokercpp">trunk/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebKit2ChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/ChangeLog (186838 => 186839)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/ChangeLog 2015-07-15 14:47:47 UTC (rev 186838)
+++ trunk/Source/WebKit2/ChangeLog 2015-07-15 16:01:32 UTC (rev 186839)
</span><span class="lines">@@ -1,3 +1,24 @@
</span><ins>+2015-07-15 Michael Catanzaro <mcatanzaro@igalia.com>
+
+ [Linux] SeccompBrokerClient should cache arbitrary file descriptors
+ https://bugs.webkit.org/show_bug.cgi?id=140068
+
+ Reviewed by Žan Doberšek.
+
+ If malloc() attempts to open /proc/sys/vm/overcommit_memory in a SIGSYS
+ signal handler, the SeccompBroker will attempt to recursively broker the
+ open() syscall. Generalize the existing code that already handles the
+ similar case where malloc() opens /sys/devices/system/cpu/online to
+ handle this situation as well.
+
+ * Shared/linux/SeccompFilters/SeccompBroker.cpp:
+ (WebKit::SIGSYSHandler):
+ (WebKit::SeccompBrokerClient::SeccompBrokerClient):
+ (WebKit::SeccompBrokerClient::~SeccompBrokerClient):
+ (WebKit::SeccompBrokerClient::handleIfOpeningCachedFile):
+ (WebKit::SeccompBrokerClient::cacheFile):
+ (WebKit::SeccompBrokerClient::handleIfOpeningOnlineCPUCount): Deleted.
+
</ins><span class="cx"> 2015-07-15 ChangSeok Oh <changseok.oh@collabora.com>
</span><span class="cx">
</span><span class="cx"> [GTK] Accelerated compositing is enabled by MiniBrowser in Wayland
</span></span></pre></div>
<a id="trunkSourceWebKit2SharedlinuxSeccompFiltersSeccompBrokercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp (186838 => 186839)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp 2015-07-15 14:47:47 UTC (rev 186838)
+++ trunk/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp 2015-07-15 16:01:32 UTC (rev 186839)
</span><span class="lines">@@ -46,7 +46,6 @@
</span><span class="cx"> #endif
</span><span class="cx">
</span><span class="cx"> static const size_t messageMaxSize = 4096;
</span><del>-static const char onlineCPUCountPath[] = "/sys/devices/system/cpu/online";
</del><span class="cx">
</span><span class="cx"> namespace WebKit {
</span><span class="cx">
</span><span class="lines">@@ -57,15 +56,19 @@
</span><span class="cx">
</span><span class="cx"> void dispatch(Syscall*) const;
</span><span class="cx">
</span><del>- bool handleIfOpeningOnlineCPUCount(mcontext_t*) const;
</del><ins>+ bool handleIfOpeningCachedFile(mcontext_t*) const;
</ins><span class="cx">
</span><span class="cx"> private:
</span><span class="cx"> SeccompBrokerClient(int socket);
</span><span class="cx">
</span><ins>+ void cacheFile(const char* path);
+
</ins><span class="cx"> int m_socket;
</span><del>- int m_onlineCPUCountFd;
</del><span class="cx">
</span><span class="cx"> mutable Mutex m_socketLock;
</span><ins>+
+ // Maps files that may be read by malloc() to open file descriptors.
+ HashMap<String, int> m_fileDescriptorCache;
</ins><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> static ssize_t sendMessage(int socket, void* data, size_t size, int fd = -1)
</span><span class="lines">@@ -142,7 +145,7 @@
</span><span class="cx">
</span><span class="cx"> SeccompBrokerClient* client = &SeccompBrokerClient::singleton();
</span><span class="cx">
</span><del>- if (client->handleIfOpeningOnlineCPUCount(&ucontext->uc_mcontext))
</del><ins>+ if (client->handleIfOpeningCachedFile(&ucontext->uc_mcontext))
</ins><span class="cx"> return;
</span><span class="cx">
</span><span class="cx"> // createFromContext might return a nullptr if it is able to resolve the
</span><span class="lines">@@ -183,15 +186,18 @@
</span><span class="cx">
</span><span class="cx"> SeccompBrokerClient::SeccompBrokerClient(int socket)
</span><span class="cx"> : m_socket(socket)
</span><del>- , m_onlineCPUCountFd(open(onlineCPUCountPath, O_RDONLY))
</del><span class="cx"> {
</span><del>- ASSERT(m_socket >= 0 && m_onlineCPUCountFd >= 0);
</del><ins>+ ASSERT(m_socket >= 0);
+
+ cacheFile("/proc/sys/vm/overcommit_memory");
+ cacheFile("/sys/devices/system/cpu/online");
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> SeccompBrokerClient::~SeccompBrokerClient()
</span><span class="cx"> {
</span><ins>+ for (int fd : m_fileDescriptorCache.values())
+ close(fd);
</ins><span class="cx"> close(m_socket);
</span><del>- close(m_onlineCPUCountFd);
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void SeccompBrokerClient::dispatch(Syscall* syscall) const
</span><span class="lines">@@ -227,25 +233,35 @@
</span><span class="cx"> syscall->setResult(result.get());
</span><span class="cx"> }
</span><span class="cx">
</span><del>-bool SeccompBrokerClient::handleIfOpeningOnlineCPUCount(mcontext_t* context) const
</del><ins>+bool SeccompBrokerClient::handleIfOpeningCachedFile(mcontext_t* context) const
</ins><span class="cx"> {
</span><span class="cx"> if (context->gregs[REG_SYSCALL] != __NR_open)
</span><span class="cx"> return false;
</span><span class="cx">
</span><span class="cx"> const char *path = reinterpret_cast<char*>(context->gregs[REG_ARG0]);
</span><del>- if (strcmp(onlineCPUCountPath, path))
</del><ins>+
+ auto iter = m_fileDescriptorCache.find(path);
+ if (iter == m_fileDescriptorCache.end())
</ins><span class="cx"> return false;
</span><span class="cx">
</span><span class="cx"> // Malloc will eventually check the number of online CPUs (i.e being
</span><span class="cx"> // scheduled) present on the system by opening a special file. If it does
</span><span class="cx"> // that in the middle of the SIGSYS signal handler, it might trigger a
</span><del>- // recursive attempt of proxying the open() syscall to the broker.
- // Because of that, we cache this resource.
- context->gregs[REG_SYSCALL] = dup(m_onlineCPUCountFd);
</del><ins>+ // recursive attempt of proxying the open() syscall to the broker. The same
+ // problem occurs if malloc() checks the memory overcommit policy. Because
+ // of that, we cache these resources.
+ context->gregs[REG_SYSCALL] = dup(iter->value);
</ins><span class="cx">
</span><span class="cx"> return true;
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+void SeccompBrokerClient::cacheFile(const char* path)
+{
+ int fd = open(path, O_RDONLY);
+ ASSERT(fd >= 0);
+ m_fileDescriptorCache.set(path, fd);
+}
+
</ins><span class="cx"> void SeccompBroker::launchProcess(SeccompFilters* filters, const SyscallPolicy& policy)
</span><span class="cx"> {
</span><span class="cx"> static bool initialized = false;
</span></span></pre>
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