From c7f2525abfecf8a57a1417837b6a809df79b299e Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 6 Mar 2019 20:22:54 -0500 Subject: [PATCH] pin iocb through aio. commit b53119f13a04879c3bf502828d99d13726639ead upstream. 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 Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman --- fs/aio.c | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 46229e663b57..10e5a8f52dce 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1016,6 +1016,9 @@ 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) { @@ -1028,7 +1031,7 @@ 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; } @@ -1061,15 +1064,18 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id) 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, @@ -1743,9 +1749,6 @@ 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 */ @@ -1776,7 +1779,6 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) if (mask) aio_poll_complete(aiocb, mask); - iocb_put(aiocb); return 0; } @@ -1867,18 +1869,21 @@ 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; -- GitLab