From b53119f13a04879c3bf502828d99d13726639ead Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 6 Mar 2019 20:22:54 -0500 Subject: [PATCH 1/9] pin iocb through aio. aio_poll() is not the only case that needs file pinned; worse, while aio_read()/aio_write() can live without pinning iocb itself, the proof is rather brittle and can easily break on later changes. Signed-off-by: Linus Torvalds Signed-off-by: Al Viro --- fs/aio.c | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 38b741aef0bf..07083fc0a24b 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1022,6 +1022,9 @@ static bool get_reqs_available(struct kioctx *ctx) /* aio_get_req * Allocate a slot for an aio request. * Returns NULL if no requests are free. + * + * The refcount is initialized to 2 - one for the async op completion, + * one for the synchronous code that does this. */ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx) { @@ -1034,7 +1037,7 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx) percpu_ref_get(&ctx->reqs); req->ki_ctx = ctx; INIT_LIST_HEAD(&req->ki_list); - refcount_set(&req->ki_refcnt, 0); + refcount_set(&req->ki_refcnt, 2); req->ki_eventfd = NULL; return req; } @@ -1067,15 +1070,18 @@ out: return ret; } +static inline void iocb_destroy(struct aio_kiocb *iocb) +{ + if (iocb->ki_filp) + fput(iocb->ki_filp); + percpu_ref_put(&iocb->ki_ctx->reqs); + kmem_cache_free(kiocb_cachep, iocb); +} + static inline void iocb_put(struct aio_kiocb *iocb) { - if (refcount_read(&iocb->ki_refcnt) == 0 || - refcount_dec_and_test(&iocb->ki_refcnt)) { - if (iocb->ki_filp) - fput(iocb->ki_filp); - percpu_ref_put(&iocb->ki_ctx->reqs); - kmem_cache_free(kiocb_cachep, iocb); - } + if (refcount_dec_and_test(&iocb->ki_refcnt)) + iocb_destroy(iocb); } static void aio_fill_event(struct io_event *ev, struct aio_kiocb *iocb, @@ -1749,9 +1755,6 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) INIT_LIST_HEAD(&req->wait.entry); init_waitqueue_func_entry(&req->wait, aio_poll_wake); - /* one for removal from waitqueue, one for this function */ - refcount_set(&aiocb->ki_refcnt, 2); - mask = vfs_poll(req->file, &apt.pt) & req->events; if (unlikely(!req->head)) { /* we did not manage to set up a waitqueue, done */ @@ -1782,7 +1785,6 @@ out: if (mask) aio_poll_complete(aiocb, mask); - iocb_put(aiocb); return 0; } @@ -1873,18 +1875,21 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, break; } + /* Done with the synchronous reference */ + iocb_put(req); + /* * If ret is 0, we'd either done aio_complete() ourselves or have * arranged for that to be done asynchronously. Anything non-zero * means that we need to destroy req ourselves. */ - if (ret) - goto out_put_req; - return 0; + if (!ret) + return 0; + out_put_req: if (req->ki_eventfd) eventfd_ctx_put(req->ki_eventfd); - iocb_put(req); + iocb_destroy(req); out_put_reqs_available: put_reqs_available(ctx, 1); return ret; From 833f4154ed560232120bc475935ee1d6a20e159f Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 11 Mar 2019 19:00:36 -0400 Subject: [PATCH 2/9] aio: fold lookup_kiocb() into its sole caller Signed-off-by: Al Viro --- fs/aio.c | 29 +++++++---------------------- 1 file changed, 7 insertions(+), 22 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 07083fc0a24b..dada3bd316d5 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -2002,24 +2002,6 @@ COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id, } #endif -/* lookup_kiocb - * Finds a given iocb for cancellation. - */ -static struct aio_kiocb * -lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb) -{ - struct aio_kiocb *kiocb; - - assert_spin_locked(&ctx->ctx_lock); - - /* TODO: use a hash or array, this sucks. */ - list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) { - if (kiocb->ki_user_iocb == iocb) - return kiocb; - } - return NULL; -} - /* sys_io_cancel: * Attempts to cancel an iocb previously passed to io_submit. If * the operation is successfully cancelled, the resulting event is @@ -2048,10 +2030,13 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, return -EINVAL; spin_lock_irq(&ctx->ctx_lock); - kiocb = lookup_kiocb(ctx, iocb); - if (kiocb) { - ret = kiocb->ki_cancel(&kiocb->rw); - list_del_init(&kiocb->ki_list); + /* TODO: use a hash or array, this sucks. */ + list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) { + if (kiocb->ki_user_iocb == iocb) { + ret = kiocb->ki_cancel(&kiocb->rw); + list_del_init(&kiocb->ki_list); + break; + } } spin_unlock_irq(&ctx->ctx_lock); From a9339b7855094ba11a97e8822ae038135e879e79 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 7 Mar 2019 19:43:45 -0500 Subject: [PATCH 3/9] aio: keep io_event in aio_kiocb We want to separate forming the resulting io_event from putting it into the ring buffer. Signed-off-by: Al Viro --- fs/aio.c | 31 +++++++++++++------------------ 1 file changed, 13 insertions(+), 18 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index dada3bd316d5..b0a8aa544e34 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -204,8 +204,7 @@ struct aio_kiocb { struct kioctx *ki_ctx; kiocb_cancel_fn *ki_cancel; - struct iocb __user *ki_user_iocb; /* user's aiocb */ - __u64 ki_user_data; /* user's data for completion */ + struct io_event ki_res; struct list_head ki_list; /* the aio core uses this * for cancellation */ @@ -1084,15 +1083,6 @@ static inline void iocb_put(struct aio_kiocb *iocb) iocb_destroy(iocb); } -static void aio_fill_event(struct io_event *ev, struct aio_kiocb *iocb, - long res, long res2) -{ - ev->obj = (u64)(unsigned long)iocb->ki_user_iocb; - ev->data = iocb->ki_user_data; - ev->res = res; - ev->res2 = res2; -} - /* aio_complete * Called when the io request on the given iocb is complete. */ @@ -1104,6 +1094,8 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2) unsigned tail, pos, head; unsigned long flags; + iocb->ki_res.res = res; + iocb->ki_res.res2 = res2; /* * Add a completion event to the ring buffer. Must be done holding * ctx->completion_lock to prevent other code from messing with the tail @@ -1120,14 +1112,14 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2) ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]); event = ev_page + pos % AIO_EVENTS_PER_PAGE; - aio_fill_event(event, iocb, res, res2); + *event = iocb->ki_res; kunmap_atomic(ev_page); flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]); - pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n", - ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data, - res, res2); + pr_debug("%p[%u]: %p: %p %Lx %Lx %Lx\n", ctx, tail, iocb, + (void __user *)(unsigned long)iocb->ki_res.obj, + iocb->ki_res.data, iocb->ki_res.res, iocb->ki_res.res2); /* after flagging the request as done, we * must never even look at it again @@ -1844,8 +1836,10 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, goto out_put_req; } - req->ki_user_iocb = user_iocb; - req->ki_user_data = iocb->aio_data; + req->ki_res.obj = (u64)(unsigned long)user_iocb; + req->ki_res.data = iocb->aio_data; + req->ki_res.res = 0; + req->ki_res.res2 = 0; switch (iocb->aio_lio_opcode) { case IOCB_CMD_PREAD: @@ -2019,6 +2013,7 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, struct aio_kiocb *kiocb; int ret = -EINVAL; u32 key; + u64 obj = (u64)(unsigned long)iocb; if (unlikely(get_user(key, &iocb->aio_key))) return -EFAULT; @@ -2032,7 +2027,7 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, spin_lock_irq(&ctx->ctx_lock); /* TODO: use a hash or array, this sucks. */ list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) { - if (kiocb->ki_user_iocb == iocb) { + if (kiocb->ki_res.obj == obj) { ret = kiocb->ki_cancel(&kiocb->rw); list_del_init(&kiocb->ki_list); break; From 2bb874c0d873d13bd9b9b9c6d7b7c4edab18c8b4 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 7 Mar 2019 19:49:55 -0500 Subject: [PATCH 4/9] aio: store event at final iocb_put() Instead of having aio_complete() set ->ki_res.{res,res2}, do that explicitly in its callers, drop the reference (as aio_complete() used to do) and delay the rest until the final iocb_put(). Signed-off-by: Al Viro --- fs/aio.c | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index b0a8aa544e34..f405e2fd8e28 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1077,16 +1077,10 @@ static inline void iocb_destroy(struct aio_kiocb *iocb) kmem_cache_free(kiocb_cachep, iocb); } -static inline void iocb_put(struct aio_kiocb *iocb) -{ - if (refcount_dec_and_test(&iocb->ki_refcnt)) - iocb_destroy(iocb); -} - /* aio_complete * Called when the io request on the given iocb is complete. */ -static void aio_complete(struct aio_kiocb *iocb, long res, long res2) +static void aio_complete(struct aio_kiocb *iocb) { struct kioctx *ctx = iocb->ki_ctx; struct aio_ring *ring; @@ -1094,8 +1088,6 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2) unsigned tail, pos, head; unsigned long flags; - iocb->ki_res.res = res; - iocb->ki_res.res2 = res2; /* * Add a completion event to the ring buffer. Must be done holding * ctx->completion_lock to prevent other code from messing with the tail @@ -1161,7 +1153,14 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2) if (waitqueue_active(&ctx->wait)) wake_up(&ctx->wait); - iocb_put(iocb); +} + +static inline void iocb_put(struct aio_kiocb *iocb) +{ + if (refcount_dec_and_test(&iocb->ki_refcnt)) { + aio_complete(iocb); + iocb_destroy(iocb); + } } /* aio_read_events_ring @@ -1435,7 +1434,9 @@ static void aio_complete_rw(struct kiocb *kiocb, long res, long res2) file_end_write(kiocb->ki_filp); } - aio_complete(iocb, res, res2); + iocb->ki_res.res = res; + iocb->ki_res.res2 = res2; + iocb_put(iocb); } static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb) @@ -1583,11 +1584,10 @@ static ssize_t aio_write(struct kiocb *req, const struct iocb *iocb, static void aio_fsync_work(struct work_struct *work) { - struct fsync_iocb *req = container_of(work, struct fsync_iocb, work); - int ret; + struct aio_kiocb *iocb = container_of(work, struct aio_kiocb, fsync.work); - ret = vfs_fsync(req->file, req->datasync); - aio_complete(container_of(req, struct aio_kiocb, fsync), ret, 0); + iocb->ki_res.res = vfs_fsync(iocb->fsync.file, iocb->fsync.datasync); + iocb_put(iocb); } static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb, @@ -1608,7 +1608,8 @@ static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb, static inline void aio_poll_complete(struct aio_kiocb *iocb, __poll_t mask) { - aio_complete(iocb, mangle_poll(mask), 0); + iocb->ki_res.res = mangle_poll(mask); + iocb_put(iocb); } static void aio_poll_complete_work(struct work_struct *work) From af5c72b1fc7a00aa484e90b0c4e0eeb582545634 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 7 Mar 2019 21:45:41 -0500 Subject: [PATCH 5/9] Fix aio_poll() races aio_poll() has to cope with several unpleasant problems: * requests that might stay around indefinitely need to be made visible for io_cancel(2); that must not be done to a request already completed, though. * in cases when ->poll() has placed us on a waitqueue, wakeup might have happened (and request completed) before ->poll() returns. * worse, in some early wakeup cases request might end up re-added into the queue later - we can't treat "woken up and currently not in the queue" as "it's not going to stick around indefinitely" * ... moreover, ->poll() might have decided not to put it on any queues to start with, and that needs to be distinguished from the previous case * ->poll() might have tried to put us on more than one queue. Only the first will succeed for aio poll, so we might end up missing wakeups. OTOH, we might very well notice that only after the wakeup hits and request gets completed (all before ->poll() gets around to the second poll_wait()). In that case it's too late to decide that we have an error. req->woken was an attempt to deal with that. Unfortunately, it was broken. What we need to keep track of is not that wakeup has happened - the thing might come back after that. It's that async reference is already gone and won't come back, so we can't (and needn't) put the request on the list of cancellables. The easiest case is "request hadn't been put on any waitqueues"; we can tell by seeing NULL apt.head, and in that case there won't be anything async. We should either complete the request ourselves (if vfs_poll() reports anything of interest) or return an error. In all other cases we get exclusion with wakeups by grabbing the queue lock. If request is currently on queue and we have something interesting from vfs_poll(), we can steal it and complete the request ourselves. If it's on queue and vfs_poll() has not reported anything interesting, we either put it on the cancellable list, or, if we know that it hadn't been put on all queues ->poll() wanted it on, we steal it and return an error. If it's _not_ on queue, it's either been already dealt with (in which case we do nothing), or there's aio_poll_complete_work() about to be executed. In that case we either put it on the cancellable list, or, if we know it hadn't been put on all queues ->poll() wanted it on, simulate what cancel would've done. It's a lot more convoluted than I'd like it to be. Single-consumer APIs suck, and unfortunately aio is not an exception... Signed-off-by: Al Viro --- fs/aio.c | 92 +++++++++++++++++++++++++------------------------------- 1 file changed, 41 insertions(+), 51 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index f405e2fd8e28..39a075992ca2 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -181,7 +181,7 @@ struct poll_iocb { struct file *file; struct wait_queue_head *head; __poll_t events; - bool woken; + bool done; bool cancelled; struct wait_queue_entry wait; struct work_struct work; @@ -1606,12 +1606,6 @@ static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb, return 0; } -static inline void aio_poll_complete(struct aio_kiocb *iocb, __poll_t mask) -{ - iocb->ki_res.res = mangle_poll(mask); - iocb_put(iocb); -} - static void aio_poll_complete_work(struct work_struct *work) { struct poll_iocb *req = container_of(work, struct poll_iocb, work); @@ -1637,9 +1631,11 @@ static void aio_poll_complete_work(struct work_struct *work) return; } list_del_init(&iocb->ki_list); + iocb->ki_res.res = mangle_poll(mask); + req->done = true; spin_unlock_irq(&ctx->ctx_lock); - aio_poll_complete(iocb, mask); + iocb_put(iocb); } /* assumes we are called with irqs disabled */ @@ -1667,31 +1663,27 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, __poll_t mask = key_to_poll(key); unsigned long flags; - req->woken = true; - /* for instances that support it check for an event match first: */ - if (mask) { - if (!(mask & req->events)) - return 0; + if (mask && !(mask & req->events)) + return 0; + list_del_init(&req->wait.entry); + + if (mask && spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) { /* * Try to complete the iocb inline if we can. Use * irqsave/irqrestore because not all filesystems (e.g. fuse) * call this function with IRQs disabled and because IRQs * have to be disabled before ctx_lock is obtained. */ - if (spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) { - list_del(&iocb->ki_list); - spin_unlock_irqrestore(&iocb->ki_ctx->ctx_lock, flags); - - list_del_init(&req->wait.entry); - aio_poll_complete(iocb, mask); - return 1; - } + list_del(&iocb->ki_list); + iocb->ki_res.res = mangle_poll(mask); + req->done = true; + spin_unlock_irqrestore(&iocb->ki_ctx->ctx_lock, flags); + iocb_put(iocb); + } else { + schedule_work(&req->work); } - - list_del_init(&req->wait.entry); - schedule_work(&req->work); return 1; } @@ -1723,6 +1715,7 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) struct kioctx *ctx = aiocb->ki_ctx; struct poll_iocb *req = &aiocb->poll; struct aio_poll_table apt; + bool cancel = false; __poll_t mask; /* reject any unknown events outside the normal event mask. */ @@ -1736,7 +1729,7 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) req->events = demangle_poll(iocb->aio_buf) | EPOLLERR | EPOLLHUP; req->head = NULL; - req->woken = false; + req->done = false; req->cancelled = false; apt.pt._qproc = aio_poll_queue_proc; @@ -1749,36 +1742,33 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) init_waitqueue_func_entry(&req->wait, aio_poll_wake); mask = vfs_poll(req->file, &apt.pt) & req->events; - if (unlikely(!req->head)) { - /* we did not manage to set up a waitqueue, done */ - goto out; - } - spin_lock_irq(&ctx->ctx_lock); - spin_lock(&req->head->lock); - if (req->woken) { - /* wake_up context handles the rest */ - mask = 0; - apt.error = 0; - } else if (mask || apt.error) { - /* if we get an error or a mask we are done */ - WARN_ON_ONCE(list_empty(&req->wait.entry)); - list_del_init(&req->wait.entry); - } else { - /* actually waiting for an event */ - list_add_tail(&aiocb->ki_list, &ctx->active_reqs); - aiocb->ki_cancel = aio_poll_cancel; + if (likely(req->head)) { + spin_lock(&req->head->lock); + if (unlikely(list_empty(&req->wait.entry))) { + if (apt.error) + cancel = true; + apt.error = 0; + mask = 0; + } + if (mask || apt.error) { + list_del_init(&req->wait.entry); + } else if (cancel) { + WRITE_ONCE(req->cancelled, true); + } else if (!req->done) { /* actually waiting for an event */ + list_add_tail(&aiocb->ki_list, &ctx->active_reqs); + aiocb->ki_cancel = aio_poll_cancel; + } + spin_unlock(&req->head->lock); + } + if (mask) { /* no async, we'd stolen it */ + aiocb->ki_res.res = mangle_poll(mask); + apt.error = 0; } - spin_unlock(&req->head->lock); spin_unlock_irq(&ctx->ctx_lock); - -out: - if (unlikely(apt.error)) - return apt.error; - if (mask) - aio_poll_complete(aiocb, mask); - return 0; + iocb_put(aiocb); + return apt.error; } static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, From 958c13ce141cd5183d3995553315d0ed27daa823 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 6 Mar 2019 18:13:00 -0500 Subject: [PATCH 6/9] make aio_read()/aio_write() return int that ssize_t is a rudiment of earlier calling conventions; it's been used only to pass 0 and -E... since last autumn. Reviewed-by: Christoph Hellwig Signed-off-by: Al Viro --- fs/aio.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 39a075992ca2..0e0b939958fa 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1513,13 +1513,13 @@ static inline void aio_rw_done(struct kiocb *req, ssize_t ret) } } -static ssize_t aio_read(struct kiocb *req, const struct iocb *iocb, +static int aio_read(struct kiocb *req, const struct iocb *iocb, bool vectored, bool compat) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; struct iov_iter iter; struct file *file; - ssize_t ret; + int ret; ret = aio_prep_rw(req, iocb); if (ret) @@ -1541,13 +1541,13 @@ static ssize_t aio_read(struct kiocb *req, const struct iocb *iocb, return ret; } -static ssize_t aio_write(struct kiocb *req, const struct iocb *iocb, +static int aio_write(struct kiocb *req, const struct iocb *iocb, bool vectored, bool compat) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; struct iov_iter iter; struct file *file; - ssize_t ret; + int ret; ret = aio_prep_rw(req, iocb); if (ret) @@ -1710,7 +1710,7 @@ aio_poll_queue_proc(struct file *file, struct wait_queue_head *head, add_wait_queue(head, &pt->iocb->poll.wait); } -static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) +static int aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) { struct kioctx *ctx = aiocb->ki_ctx; struct poll_iocb *req = &aiocb->poll; @@ -1775,7 +1775,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, struct iocb __user *user_iocb, bool compat) { struct aio_kiocb *req; - ssize_t ret; + int ret; /* enforce forwards compatibility on users */ if (unlikely(iocb->aio_reserved2)) { From 7425970347a21204632a27ed28978cf875f205b2 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 6 Mar 2019 18:18:31 -0500 Subject: [PATCH 7/9] aio: move dropping ->ki_eventfd into iocb_destroy() no reason to duplicate that... Signed-off-by: Al Viro --- fs/aio.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 0e0b939958fa..d3837f607d09 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1071,6 +1071,8 @@ out: static inline void iocb_destroy(struct aio_kiocb *iocb) { + if (iocb->ki_eventfd) + eventfd_ctx_put(iocb->ki_eventfd); if (iocb->ki_filp) fput(iocb->ki_filp); percpu_ref_put(&iocb->ki_ctx->reqs); @@ -1138,10 +1140,8 @@ static void aio_complete(struct aio_kiocb *iocb) * eventfd. The eventfd_signal() function is safe to be called * from IRQ context. */ - if (iocb->ki_eventfd) { + if (iocb->ki_eventfd) eventfd_signal(iocb->ki_eventfd, 1); - eventfd_ctx_put(iocb->ki_eventfd); - } /* * We have to order our ring_info tail store above and test @@ -1807,18 +1807,19 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, goto out_put_req; if (iocb->aio_flags & IOCB_FLAG_RESFD) { + struct eventfd_ctx *eventfd; /* * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an * instance of the file* now. The file descriptor must be * an eventfd() fd, and will be signaled for each completed * event using the eventfd_signal() function. */ - req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd); - if (IS_ERR(req->ki_eventfd)) { - ret = PTR_ERR(req->ki_eventfd); - req->ki_eventfd = NULL; + eventfd = eventfd_ctx_fdget(iocb->aio_resfd); + if (IS_ERR(eventfd)) { + ret = PTR_ERR(eventfd); goto out_put_req; } + req->ki_eventfd = eventfd; } ret = put_user(KIOCB_KEY, &user_iocb->aio_key); @@ -1872,8 +1873,6 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, return 0; out_put_req: - if (req->ki_eventfd) - eventfd_ctx_put(req->ki_eventfd); iocb_destroy(req); out_put_reqs_available: put_reqs_available(ctx, 1); From fa0ca2aee3bec899f9b9e753baf3808d1b0628f6 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 6 Mar 2019 18:21:08 -0500 Subject: [PATCH 8/9] deal with get_reqs_available() in aio_get_req() itself simplifies the caller Reviewed-by: Christoph Hellwig Signed-off-by: Al Viro --- fs/aio.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index d3837f607d09..eee4b4cfb66f 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1033,6 +1033,11 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx) if (unlikely(!req)) return NULL; + if (unlikely(!get_reqs_available(ctx))) { + kfree(req); + return NULL; + } + percpu_ref_get(&ctx->reqs); req->ki_ctx = ctx; INIT_LIST_HEAD(&req->ki_list); @@ -1793,13 +1798,9 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, return -EINVAL; } - if (!get_reqs_available(ctx)) - return -EAGAIN; - - ret = -EAGAIN; req = aio_get_req(ctx); if (unlikely(!req)) - goto out_put_reqs_available; + return -EAGAIN; req->ki_filp = fget(iocb->aio_fildes); ret = -EBADF; @@ -1874,7 +1875,6 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, out_put_req: iocb_destroy(req); -out_put_reqs_available: put_reqs_available(ctx, 1); return ret; } From 7316b49c2a117ca0611bc9af779d2108b764a7f9 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 6 Mar 2019 18:24:51 -0500 Subject: [PATCH 9/9] aio: move sanity checks and request allocation to io_submit_one() makes for somewhat cleaner control flow in __io_submit_one() Signed-off-by: Al Viro --- fs/aio.c | 119 +++++++++++++++++++++++++------------------------------ 1 file changed, 53 insertions(+), 66 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index eee4b4cfb66f..a4cc2a1cccb7 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1777,35 +1777,12 @@ static int aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) } static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, - struct iocb __user *user_iocb, bool compat) + struct iocb __user *user_iocb, struct aio_kiocb *req, + bool compat) { - struct aio_kiocb *req; - int ret; - - /* enforce forwards compatibility on users */ - if (unlikely(iocb->aio_reserved2)) { - pr_debug("EINVAL: reserve field set\n"); - return -EINVAL; - } - - /* prevent overflows */ - if (unlikely( - (iocb->aio_buf != (unsigned long)iocb->aio_buf) || - (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) || - ((ssize_t)iocb->aio_nbytes < 0) - )) { - pr_debug("EINVAL: overflow check\n"); - return -EINVAL; - } - - req = aio_get_req(ctx); - if (unlikely(!req)) - return -EAGAIN; - req->ki_filp = fget(iocb->aio_fildes); - ret = -EBADF; if (unlikely(!req->ki_filp)) - goto out_put_req; + return -EBADF; if (iocb->aio_flags & IOCB_FLAG_RESFD) { struct eventfd_ctx *eventfd; @@ -1816,17 +1793,15 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, * event using the eventfd_signal() function. */ eventfd = eventfd_ctx_fdget(iocb->aio_resfd); - if (IS_ERR(eventfd)) { - ret = PTR_ERR(eventfd); - goto out_put_req; - } + if (IS_ERR(eventfd)) + return PTR_ERR(req->ki_eventfd); + req->ki_eventfd = eventfd; } - ret = put_user(KIOCB_KEY, &user_iocb->aio_key); - if (unlikely(ret)) { + if (unlikely(put_user(KIOCB_KEY, &user_iocb->aio_key))) { pr_debug("EFAULT: aio_key\n"); - goto out_put_req; + return -EFAULT; } req->ki_res.obj = (u64)(unsigned long)user_iocb; @@ -1836,58 +1811,70 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, switch (iocb->aio_lio_opcode) { case IOCB_CMD_PREAD: - ret = aio_read(&req->rw, iocb, false, compat); - break; + return aio_read(&req->rw, iocb, false, compat); case IOCB_CMD_PWRITE: - ret = aio_write(&req->rw, iocb, false, compat); - break; + return aio_write(&req->rw, iocb, false, compat); case IOCB_CMD_PREADV: - ret = aio_read(&req->rw, iocb, true, compat); - break; + return aio_read(&req->rw, iocb, true, compat); case IOCB_CMD_PWRITEV: - ret = aio_write(&req->rw, iocb, true, compat); - break; + return aio_write(&req->rw, iocb, true, compat); case IOCB_CMD_FSYNC: - ret = aio_fsync(&req->fsync, iocb, false); - break; + return aio_fsync(&req->fsync, iocb, false); case IOCB_CMD_FDSYNC: - ret = aio_fsync(&req->fsync, iocb, true); - break; + return aio_fsync(&req->fsync, iocb, true); case IOCB_CMD_POLL: - ret = aio_poll(req, iocb); - break; + return aio_poll(req, iocb); default: pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode); - ret = -EINVAL; - break; + return -EINVAL; } - - /* Done with the synchronous reference */ - iocb_put(req); - - /* - * If ret is 0, we'd either done aio_complete() ourselves or have - * arranged for that to be done asynchronously. Anything non-zero - * means that we need to destroy req ourselves. - */ - if (!ret) - return 0; - -out_put_req: - iocb_destroy(req); - put_reqs_available(ctx, 1); - return ret; } static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, bool compat) { + struct aio_kiocb *req; struct iocb iocb; + int err; if (unlikely(copy_from_user(&iocb, user_iocb, sizeof(iocb)))) return -EFAULT; - return __io_submit_one(ctx, &iocb, user_iocb, compat); + /* enforce forwards compatibility on users */ + if (unlikely(iocb.aio_reserved2)) { + pr_debug("EINVAL: reserve field set\n"); + return -EINVAL; + } + + /* prevent overflows */ + if (unlikely( + (iocb.aio_buf != (unsigned long)iocb.aio_buf) || + (iocb.aio_nbytes != (size_t)iocb.aio_nbytes) || + ((ssize_t)iocb.aio_nbytes < 0) + )) { + pr_debug("EINVAL: overflow check\n"); + return -EINVAL; + } + + req = aio_get_req(ctx); + if (unlikely(!req)) + return -EAGAIN; + + err = __io_submit_one(ctx, &iocb, user_iocb, req, compat); + + /* Done with the synchronous reference */ + iocb_put(req); + + /* + * If err is 0, we'd either done aio_complete() ourselves or have + * arranged for that to be done asynchronously. Anything non-zero + * means that we need to destroy req ourselves. + */ + if (unlikely(err)) { + iocb_destroy(req); + put_reqs_available(ctx, 1); + } + return err; } /* sys_io_submit: