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https://github.com/edk2-porting/linux-next.git
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b5e683d5ca
eventfd use cases from aio and io_uring can deadlock due to circular or resursive calling, when eventfd_signal() tries to grab the waitqueue lock. On top of that, it's also possible to construct notification chains that are deep enough that we could blow the stack. Add a percpu counter that tracks the percpu recursion depth, warn if we exceed it. The counter is also exposed so that users of eventfd_signal() can do the right thing if it's non-zero in the context where it is called. Cc: stable@vger.kernel.org # 4.19+ Signed-off-by: Jens Axboe <axboe@kernel.dk>
89 lines
2.0 KiB
C
89 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* include/linux/eventfd.h
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*
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* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
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*
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*/
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#ifndef _LINUX_EVENTFD_H
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#define _LINUX_EVENTFD_H
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#include <linux/fcntl.h>
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#include <linux/wait.h>
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#include <linux/err.h>
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#include <linux/percpu-defs.h>
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#include <linux/percpu.h>
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/*
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* CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
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* new flags, since they might collide with O_* ones. We want
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* to re-use O_* flags that couldn't possibly have a meaning
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* from eventfd, in order to leave a free define-space for
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* shared O_* flags.
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*/
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#define EFD_SEMAPHORE (1 << 0)
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#define EFD_CLOEXEC O_CLOEXEC
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#define EFD_NONBLOCK O_NONBLOCK
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#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
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#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
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struct eventfd_ctx;
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struct file;
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#ifdef CONFIG_EVENTFD
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void eventfd_ctx_put(struct eventfd_ctx *ctx);
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struct file *eventfd_fget(int fd);
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struct eventfd_ctx *eventfd_ctx_fdget(int fd);
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struct eventfd_ctx *eventfd_ctx_fileget(struct file *file);
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__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n);
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int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
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__u64 *cnt);
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DECLARE_PER_CPU(int, eventfd_wake_count);
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static inline bool eventfd_signal_count(void)
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{
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return this_cpu_read(eventfd_wake_count);
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}
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#else /* CONFIG_EVENTFD */
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/*
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* Ugly ugly ugly error layer to support modules that uses eventfd but
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* pretend to work in !CONFIG_EVENTFD configurations. Namely, AIO.
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*/
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static inline struct eventfd_ctx *eventfd_ctx_fdget(int fd)
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{
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return ERR_PTR(-ENOSYS);
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}
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static inline int eventfd_signal(struct eventfd_ctx *ctx, int n)
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{
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return -ENOSYS;
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}
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static inline void eventfd_ctx_put(struct eventfd_ctx *ctx)
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{
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}
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static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx,
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wait_queue_entry_t *wait, __u64 *cnt)
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{
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return -ENOSYS;
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}
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static inline bool eventfd_signal_count(void)
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{
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return false;
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}
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#endif
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#endif /* _LINUX_EVENTFD_H */
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