From 3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 2 Sep 2026 15:31:14 -0700 Subject: treewide: refresh kmalloc_obj() conversions This is another run of the Coccinelle script for converting kmalloc() family of allocations to kmalloc_obj() via the existing rules in scripts/coccinelle/api/kmalloc_objs.cocci This catches both the set of kmalloc() uses added since the first kmalloc_obj() conversions in v7.0 and adds a large group missed in the first pass due to Coccinelle not interacting well with the cleanup.h scoped_...() family of macros[1]. I worked around this with spatch's "--macro-file" argument to a file with all the scoped_...() macros mapped to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control flow indicator I could find. Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc, riscv, and s390 with no new warnings. Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1] Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2] Signed-off-by: Kees Cook --- io_uring/eventfd.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 io_uring/eventfd.c (limited to 'io_uring/eventfd.c') diff --git a/io_uring/eventfd.c b/io_uring/eventfd.c new file mode 100644 index 000000000..63fe6e5d7 --- /dev/null +++ b/io_uring/eventfd.c @@ -0,0 +1,173 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include + +#include "io-wq.h" +#include "eventfd.h" + +struct io_ev_fd { + struct eventfd_ctx *cq_ev_fd; + unsigned int eventfd_async; + /* protected by ->completion_lock */ + unsigned last_cq_tail; + refcount_t refs; + atomic_t ops; + struct rcu_head rcu; +}; + +enum { + IO_EVENTFD_OP_SIGNAL_BIT, +}; + +static void io_eventfd_free(struct rcu_head *rcu) +{ + struct io_ev_fd *ev_fd = container_of(rcu, struct io_ev_fd, rcu); + + eventfd_ctx_put(ev_fd->cq_ev_fd); + kfree(ev_fd); +} + +static void io_eventfd_put(struct io_ev_fd *ev_fd) +{ + if (refcount_dec_and_test(&ev_fd->refs)) + call_rcu(&ev_fd->rcu, io_eventfd_free); +} + +static void io_eventfd_do_signal(struct rcu_head *rcu) +{ + struct io_ev_fd *ev_fd = container_of(rcu, struct io_ev_fd, rcu); + + atomic_andnot(BIT(IO_EVENTFD_OP_SIGNAL_BIT), &ev_fd->ops); + eventfd_signal_mask(ev_fd->cq_ev_fd, EPOLL_URING_WAKE); + io_eventfd_put(ev_fd); +} + +/* + * Returns true if the caller should put the ev_fd reference, false if not. + */ +static bool __io_eventfd_signal(struct io_ev_fd *ev_fd, bool defer) +{ + if (!defer && eventfd_signal_allowed()) { + eventfd_signal_mask(ev_fd->cq_ev_fd, EPOLL_URING_WAKE); + return true; + } + if (!atomic_fetch_or(BIT(IO_EVENTFD_OP_SIGNAL_BIT), &ev_fd->ops)) { + call_rcu_hurry(&ev_fd->rcu, io_eventfd_do_signal); + return false; + } + return true; +} + +/* + * Trigger if eventfd_async isn't set, or if it's set and the caller is + * an async worker. + */ +static bool io_eventfd_trigger(struct io_ev_fd *ev_fd) +{ + return !ev_fd->eventfd_async || io_wq_current_is_worker(); +} + +void io_eventfd_signal(struct io_ring_ctx *ctx, bool cqe_event, bool defer) +{ + bool skip = false; + struct io_ev_fd *ev_fd; + struct io_rings *rings; + + guard(rcu)(); + + rings = rcu_dereference(ctx->rings_rcu); + if (!rings) + return; + if (READ_ONCE(rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED) + return; + ev_fd = rcu_dereference(ctx->io_ev_fd); + /* + * Check again if ev_fd exists in case an io_eventfd_unregister call + * completed between the NULL check of ctx->io_ev_fd at the start of + * the function and rcu_read_lock. + */ + if (!ev_fd) + return; + if (!io_eventfd_trigger(ev_fd) || !refcount_inc_not_zero(&ev_fd->refs)) + return; + + if (cqe_event) { + /* + * Eventfd should only get triggered when at least one event + * has been posted. Some applications rely on the eventfd + * notification count only changing IFF a new CQE has been + * added to the CQ ring. There's no dependency on 1:1 + * relationship between how many times this function is called + * (and hence the eventfd count) and number of CQEs posted to + * the CQ ring. + */ + spin_lock(&ctx->completion_lock); + skip = ctx->cached_cq_tail == ev_fd->last_cq_tail; + ev_fd->last_cq_tail = ctx->cached_cq_tail; + spin_unlock(&ctx->completion_lock); + } + + if (skip || __io_eventfd_signal(ev_fd, defer)) + io_eventfd_put(ev_fd); +} + +int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg, + unsigned int eventfd_async) +{ + struct io_ev_fd *ev_fd; + __s32 __user *fds = arg; + int fd; + + ev_fd = rcu_dereference_protected(ctx->io_ev_fd, + lockdep_is_held(&ctx->uring_lock)); + if (ev_fd) + return -EBUSY; + + if (copy_from_user(&fd, fds, sizeof(*fds))) + return -EFAULT; + + ev_fd = kmalloc_obj(*ev_fd); + if (!ev_fd) + return -ENOMEM; + + ev_fd->cq_ev_fd = eventfd_ctx_fdget(fd); + if (IS_ERR(ev_fd->cq_ev_fd)) { + int ret = PTR_ERR(ev_fd->cq_ev_fd); + + kfree(ev_fd); + return ret; + } + + spin_lock(&ctx->completion_lock); + ev_fd->last_cq_tail = ctx->cached_cq_tail; + spin_unlock(&ctx->completion_lock); + + ev_fd->eventfd_async = eventfd_async; + ctx->int_flags |= IO_RING_F_HAS_EVFD; + refcount_set(&ev_fd->refs, 1); + atomic_set(&ev_fd->ops, 0); + rcu_assign_pointer(ctx->io_ev_fd, ev_fd); + return 0; +} + +int io_eventfd_unregister(struct io_ring_ctx *ctx) +{ + struct io_ev_fd *ev_fd; + + ev_fd = rcu_dereference_protected(ctx->io_ev_fd, + lockdep_is_held(&ctx->uring_lock)); + if (ev_fd) { + ctx->int_flags &= ~IO_RING_F_HAS_EVFD; + rcu_assign_pointer(ctx->io_ev_fd, NULL); + io_eventfd_put(ev_fd); + return 0; + } + + return -ENXIO; +} -- cgit v1.3.1