--- v9
+++ v5
@@ -1,55 +1,57 @@
-Export receive_fd() so that some modules can use
-it to pass file descriptor between processes without
-missing any security stuffs.
+Increase the recursion depth of eventfd_signal() to 1. This
+is the maximum recursion depth we have found so far, which
+can be triggered with the following call chain:
+ kvm_io_bus_write [kvm]
+ --> ioeventfd_write [kvm]
+ --> eventfd_signal [eventfd]
+ --> vhost_poll_wakeup [vhost]
+ --> vduse_vdpa_kick_vq [vduse]
+ --> eventfd_signal [eventfd]
+
+Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
---
- fs/file.c | 6 ++++++
- include/linux/file.h | 7 +++----
- 2 files changed, 9 insertions(+), 4 deletions(-)
+ fs/eventfd.c | 2 +-
+ include/linux/eventfd.h | 5 ++++-
+ 2 files changed, 5 insertions(+), 2 deletions(-)
-diff --git a/fs/file.c b/fs/file.c
-index 86dc9956af32..210e540672aa 100644
---- a/fs/file.c
-+++ b/fs/file.c
-@@ -1134,6 +1134,12 @@ int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
- return new_fd;
+diff --git a/fs/eventfd.c b/fs/eventfd.c
+index e265b6dd4f34..cc7cd1dbedd3 100644
+--- a/fs/eventfd.c
++++ b/fs/eventfd.c
+@@ -71,7 +71,7 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
+ * it returns true, the eventfd_signal() call should be deferred to a
+ * safe context.
+ */
+- if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count)))
++ if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count) > EFD_WAKE_DEPTH))
+ return 0;
+
+ spin_lock_irqsave(&ctx->wqh.lock, flags);
+diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
+index fa0a524baed0..886d99cd38ef 100644
+--- a/include/linux/eventfd.h
++++ b/include/linux/eventfd.h
+@@ -29,6 +29,9 @@
+ #define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
+ #define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
+
++/* Maximum recursion depth */
++#define EFD_WAKE_DEPTH 1
++
+ struct eventfd_ctx;
+ struct file;
+
+@@ -47,7 +50,7 @@ DECLARE_PER_CPU(int, eventfd_wake_count);
+
+ static inline bool eventfd_signal_count(void)
+ {
+- return this_cpu_read(eventfd_wake_count);
++ return this_cpu_read(eventfd_wake_count) > EFD_WAKE_DEPTH;
}
-+int receive_fd(struct file *file, unsigned int o_flags)
-+{
-+ return __receive_fd(file, NULL, o_flags);
-+}
-+EXPORT_SYMBOL_GPL(receive_fd);
-+
- static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
- {
- int err = -EBADF;
-diff --git a/include/linux/file.h b/include/linux/file.h
-index 2de2e4613d7b..51e830b4fe3a 100644
---- a/include/linux/file.h
-+++ b/include/linux/file.h
-@@ -94,6 +94,9 @@ extern void fd_install(unsigned int fd, struct file *file);
-
- extern int __receive_fd(struct file *file, int __user *ufd,
- unsigned int o_flags);
-+
-+extern int receive_fd(struct file *file, unsigned int o_flags);
-+
- static inline int receive_fd_user(struct file *file, int __user *ufd,
- unsigned int o_flags)
- {
-@@ -101,10 +104,6 @@ static inline int receive_fd_user(struct file *file, int __user *ufd,
- return -EFAULT;
- return __receive_fd(file, ufd, o_flags);
- }
--static inline int receive_fd(struct file *file, unsigned int o_flags)
--{
-- return __receive_fd(file, NULL, o_flags);
--}
- int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags);
-
- extern void flush_delayed_fput(void);
+ #else /* CONFIG_EVENTFD */
--
2.11.0