c4360a84fc
- nbd/server: CVE-2024-7409: Close stray clients at server-stop - main-loop.h: introduce qemu_in_main_thread() - aio-wait.h: introduce AIO_WAIT_WHILE_UNLOCKED - nbd/server: CVE-2024-7409: Drop non-negotiating clients - nbd/server: CVE-2024-7409: Cap default max-connections to 100 - nbd: Add max-connections to nbd-server-start - nbd/server: Plumb in new args to nbd_client_add() - nbd: Minor style and typo fixes Signed-off-by: Jiabo Feng <fengjiabo1@huawei.com>
117 lines
4.0 KiB
Diff
117 lines
4.0 KiB
Diff
From f0cbb49e2a44bcf5a515922b96853acc1bed3b79 Mon Sep 17 00:00:00 2001
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From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Date: Thu, 3 Mar 2022 10:15:46 -0500
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Subject: [PATCH 7/8] main-loop.h: introduce qemu_in_main_thread()
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When invoked from the main loop, this function is the same
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as qemu_mutex_iothread_locked, and returns true if the BQL is held.
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When invoked from iothreads or tests, it returns true only
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if the current AioContext is the Main Loop.
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This essentially just extends qemu_mutex_iothread_locked to work
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also in unit tests or other users like storage-daemon, that run
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in the Main Loop but end up using the implementation in
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stubs/iothread-lock.c.
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Using qemu_mutex_iothread_locked in unit tests defaults to false
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because they use the implementation in stubs/iothread-lock,
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making all assertions added in next patches fail despite the
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AioContext is still the main loop.
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See the comment in the function header for more information.
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Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Message-Id: <20220303151616.325444-2-eesposit@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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cpus.c | 5 +++++
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include/qemu/main-loop.h | 24 ++++++++++++++++++++++++
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stubs/Makefile.objs | 1 +
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stubs/iothread-lock-block.c | 8 ++++++++
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4 files changed, 38 insertions(+)
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create mode 100644 stubs/iothread-lock-block.c
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diff --git a/cpus.c b/cpus.c
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index b2a26a1f11..d2d486129d 100644
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--- a/cpus.c
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+++ b/cpus.c
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@@ -1848,6 +1848,11 @@ bool qemu_mutex_iothread_locked(void)
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return iothread_locked;
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}
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+bool qemu_in_main_thread(void)
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+{
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+ return qemu_mutex_iothread_locked();
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+}
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+
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/*
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* The BQL is taken from so many places that it is worth profiling the
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* callers directly, instead of funneling them all through a single function.
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diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
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index cba048bc82..42d65cf270 100644
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--- a/include/qemu/main-loop.h
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+++ b/include/qemu/main-loop.h
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@@ -260,9 +260,33 @@ int qemu_add_child_watch(pid_t pid);
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* must always be taken outside other locks. This function helps
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* functions take different paths depending on whether the current
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* thread is running within the main loop mutex.
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+ *
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+ * This function should never be used in the block layer, because
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+ * unit tests, block layer tools and qemu-storage-daemon do not
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+ * have a BQL.
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+ * Please instead refer to qemu_in_main_thread().
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*/
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bool qemu_mutex_iothread_locked(void);
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+/**
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+ * qemu_in_main_thread: return whether it's possible to safely access
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+ * the global state of the block layer.
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+ *
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+ * Global state of the block layer is not accessible from I/O threads
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+ * or worker threads; only from threads that "own" the default
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+ * AioContext that qemu_get_aio_context() returns. For tests, block
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+ * layer tools and qemu-storage-daemon there is a designated thread that
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+ * runs the event loop for qemu_get_aio_context(), and that is the
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+ * main thread.
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+ *
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+ * For emulators, however, any thread that holds the BQL can act
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+ * as the block layer main thread; this will be any of the actual
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+ * main thread, the vCPU threads or the RCU thread.
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+ *
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+ * For clarity, do not use this function outside the block layer.
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+ */
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+bool qemu_in_main_thread(void);
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+
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/**
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* qemu_mutex_lock_iothread: Lock the main loop mutex.
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*
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diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
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index 9c7393b08c..e748ccd323 100644
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--- a/stubs/Makefile.objs
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+++ b/stubs/Makefile.objs
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@@ -11,6 +11,7 @@ stub-obj-y += gdbstub.o
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stub-obj-y += get-vm-name.o
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stub-obj-y += iothread.o
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stub-obj-y += iothread-lock.o
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+stub-obj-y += iothread-lock-block.o
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stub-obj-y += is-daemonized.o
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stub-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
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stub-obj-y += machine-init-done.o
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diff --git a/stubs/iothread-lock-block.c b/stubs/iothread-lock-block.c
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new file mode 100644
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index 0000000000..c88ed70462
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--- /dev/null
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+++ b/stubs/iothread-lock-block.c
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@@ -0,0 +1,8 @@
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+#include "qemu/osdep.h"
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+#include "qemu/main-loop.h"
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+
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+bool qemu_in_main_thread(void)
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+{
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+ return qemu_get_current_aio_context() == qemu_get_aio_context();
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+}
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+
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--
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2.45.1.windows.1
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