From 09bb839434bd845c01da3d159b0c126fe7fa90da Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 13 Mar 2019 12:39:28 -0600 Subject: [PATCH] io_uring: fix fget/fput handling This isn't a straight port of commit 84c4e1f89fef for aio.c, since io_uring doesn't use files in exactly the same way. But it's pretty close. See the commit message for that commit. This essentially fixes a use-after-free with the poll command handling, but it takes cue from Linus's approach to just simplifying the file handling. We move the setup of the file into a higher level location, so the individual commands don't have to deal with it. And then we release the reference when we free the associated io_kiocb. Fixes: 221c5eb23382 ("io_uring: add support for IORING_OP_POLL") Signed-off-by: Jens Axboe --- fs/io_uring.c | 230 +++++++++++++++++++++++++--------------------------------- 1 file changed, 97 insertions(+), 133 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index d259e8a..c08fa62 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -189,6 +189,10 @@ struct sqe_submit { bool needs_fixed_file; }; +/* + * First field must be the file pointer in all the + * iocb unions! See also 'struct kiocb' in + */ struct io_poll_iocb { struct file *file; struct wait_queue_head *head; @@ -198,8 +202,15 @@ struct io_poll_iocb { struct wait_queue_entry wait; }; +/* + * NOTE! Each of the iocb union members has the file pointer + * as the first entry in their struct definition. So you can + * access the file pointer through any of the sub-structs, + * or directly as just 'ki_filp' in this struct. + */ struct io_kiocb { union { + struct file *file; struct kiocb rw; struct io_poll_iocb poll; }; @@ -431,6 +442,8 @@ static void io_free_req_many(struct io_ring_ctx *ctx, void **reqs, int *nr) static void io_free_req(struct io_kiocb *req) { + if (req->file && !(req->flags & REQ_F_FIXED_FILE)) + fput(req->file); io_ring_drop_ctx_refs(req->ctx, 1); kmem_cache_free(req_cachep, req); } @@ -448,45 +461,34 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events, struct list_head *done) { void *reqs[IO_IOPOLL_BATCH]; - int file_count, to_free; - struct file *file = NULL; struct io_kiocb *req; + int to_free; - file_count = to_free = 0; + to_free = 0; while (!list_empty(done)) { req = list_first_entry(done, struct io_kiocb, list); list_del(&req->list); io_cqring_fill_event(ctx, req->user_data, req->error, 0); - - if (refcount_dec_and_test(&req->refs)) - reqs[to_free++] = req; (*nr_events)++; - /* - * Batched puts of the same file, to avoid dirtying the - * file usage count multiple times, if avoidable. - */ - if (!(req->flags & REQ_F_FIXED_FILE)) { - if (!file) { - file = req->rw.ki_filp; - file_count = 1; - } else if (file == req->rw.ki_filp) { - file_count++; + if (refcount_dec_and_test(&req->refs)) { + /* If we're not using fixed files, we have to pair the + * completion part with the file put. Use regular + * completions for those, only batch free for fixed + * file. + */ + if (req->flags & REQ_F_FIXED_FILE) { + reqs[to_free++] = req; + if (to_free == ARRAY_SIZE(reqs)) + io_free_req_many(ctx, reqs, &to_free); } else { - fput_many(file, file_count); - file = req->rw.ki_filp; - file_count = 1; + io_free_req(req); } } - - if (to_free == ARRAY_SIZE(reqs)) - io_free_req_many(ctx, reqs, &to_free); } - io_commit_cqring(ctx); - if (file) - fput_many(file, file_count); + io_commit_cqring(ctx); io_free_req_many(ctx, reqs, &to_free); } @@ -609,19 +611,12 @@ static void kiocb_end_write(struct kiocb *kiocb) } } -static void io_fput(struct io_kiocb *req) -{ - if (!(req->flags & REQ_F_FIXED_FILE)) - fput(req->rw.ki_filp); -} - static void io_complete_rw(struct kiocb *kiocb, long res, long res2) { struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); kiocb_end_write(kiocb); - io_fput(req); io_cqring_add_event(req->ctx, req->user_data, res, 0); io_put_req(req); } @@ -738,31 +733,18 @@ static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s, const struct io_uring_sqe *sqe = s->sqe; struct io_ring_ctx *ctx = req->ctx; struct kiocb *kiocb = &req->rw; - unsigned ioprio, flags; - int fd, ret; + unsigned ioprio; + int ret; + if (!req->file) + return -EBADF; /* For -EAGAIN retry, everything is already prepped */ if (req->flags & REQ_F_PREPPED) return 0; - flags = READ_ONCE(sqe->flags); - fd = READ_ONCE(sqe->fd); + if (force_nonblock && !io_file_supports_async(req->file)) + force_nonblock = false; - if (flags & IOSQE_FIXED_FILE) { - if (unlikely(!ctx->user_files || - (unsigned) fd >= ctx->nr_user_files)) - return -EBADF; - kiocb->ki_filp = ctx->user_files[fd]; - req->flags |= REQ_F_FIXED_FILE; - } else { - if (s->needs_fixed_file) - return -EBADF; - kiocb->ki_filp = io_file_get(state, fd); - if (unlikely(!kiocb->ki_filp)) - return -EBADF; - if (force_nonblock && !io_file_supports_async(kiocb->ki_filp)) - force_nonblock = false; - } kiocb->ki_pos = READ_ONCE(sqe->off); kiocb->ki_flags = iocb_flags(kiocb->ki_filp); kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp)); @@ -771,7 +753,7 @@ static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s, if (ioprio) { ret = ioprio_check_cap(ioprio); if (ret) - goto out_fput; + return ret; kiocb->ki_ioprio = ioprio; } else @@ -779,39 +761,26 @@ static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s, ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags)); if (unlikely(ret)) - goto out_fput; + return ret; if (force_nonblock) { kiocb->ki_flags |= IOCB_NOWAIT; req->flags |= REQ_F_FORCE_NONBLOCK; } if (ctx->flags & IORING_SETUP_IOPOLL) { - ret = -EOPNOTSUPP; if (!(kiocb->ki_flags & IOCB_DIRECT) || !kiocb->ki_filp->f_op->iopoll) - goto out_fput; + return -EOPNOTSUPP; req->error = 0; kiocb->ki_flags |= IOCB_HIPRI; kiocb->ki_complete = io_complete_rw_iopoll; } else { - if (kiocb->ki_flags & IOCB_HIPRI) { - ret = -EINVAL; - goto out_fput; - } + if (kiocb->ki_flags & IOCB_HIPRI) + return -EINVAL; kiocb->ki_complete = io_complete_rw; } req->flags |= REQ_F_PREPPED; return 0; -out_fput: - if (!(flags & IOSQE_FIXED_FILE)) { - /* - * in case of error, we didn't use this file reference. drop it. - */ - if (state) - state->used_refs--; - io_file_put(state, kiocb->ki_filp); - } - return ret; } static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret) @@ -968,16 +937,14 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s, return ret; file = kiocb->ki_filp; - ret = -EBADF; if (unlikely(!(file->f_mode & FMODE_READ))) - goto out_fput; - ret = -EINVAL; + return -EBADF; if (unlikely(!file->f_op->read_iter)) - goto out_fput; + return -EINVAL; ret = io_import_iovec(req->ctx, READ, s, &iovec, &iter); if (ret) - goto out_fput; + return ret; iov_count = iov_iter_count(&iter); ret = rw_verify_area(READ, file, &kiocb->ki_pos, iov_count); @@ -999,10 +966,6 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s, } } kfree(iovec); -out_fput: - /* Hold on to the file for -EAGAIN */ - if (unlikely(ret && ret != -EAGAIN)) - io_fput(req); return ret; } @@ -1020,17 +983,15 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s, if (ret) return ret; - ret = -EBADF; file = kiocb->ki_filp; if (unlikely(!(file->f_mode & FMODE_WRITE))) - goto out_fput; - ret = -EINVAL; + return -EBADF; if (unlikely(!file->f_op->write_iter)) - goto out_fput; + return -EINVAL; ret = io_import_iovec(req->ctx, WRITE, s, &iovec, &iter); if (ret) - goto out_fput; + return ret; iov_count = iov_iter_count(&iter); @@ -1062,10 +1023,6 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s, } out_free: kfree(iovec); -out_fput: - /* Hold on to the file for -EAGAIN */ - if (unlikely(ret && ret != -EAGAIN)) - io_fput(req); return ret; } @@ -1080,16 +1037,6 @@ static int io_nop(struct io_kiocb *req, u64 user_data) if (unlikely(ctx->flags & IORING_SETUP_IOPOLL)) return -EINVAL; - /* - * Twilight zone - it's possible that someone issued an opcode that - * has a file attached, then got -EAGAIN on submission, and changed - * the sqe before we retried it from async context. Avoid dropping - * a file reference for this malicious case, and flag the error. - */ - if (req->rw.ki_filp) { - err = -EBADF; - io_fput(req); - } io_cqring_add_event(ctx, user_data, err, 0); io_put_req(req); return 0; @@ -1098,9 +1045,9 @@ static int io_nop(struct io_kiocb *req, u64 user_data) static int io_prep_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe) { struct io_ring_ctx *ctx = req->ctx; - unsigned flags; - int fd; + if (!req->file) + return -EBADF; /* Prep already done (EAGAIN retry) */ if (req->flags & REQ_F_PREPPED) return 0; @@ -1110,20 +1057,6 @@ static int io_prep_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe) if (unlikely(sqe->addr || sqe->ioprio || sqe->buf_index)) return -EINVAL; - fd = READ_ONCE(sqe->fd); - flags = READ_ONCE(sqe->flags); - - if (flags & IOSQE_FIXED_FILE) { - if (unlikely(!ctx->user_files || fd >= ctx->nr_user_files)) - return -EBADF; - req->rw.ki_filp = ctx->user_files[fd]; - req->flags |= REQ_F_FIXED_FILE; - } else { - req->rw.ki_filp = fget(fd); - if (unlikely(!req->rw.ki_filp)) - return -EBADF; - } - req->flags |= REQ_F_PREPPED; return 0; } @@ -1153,7 +1086,6 @@ static int io_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe, end > 0 ? end : LLONG_MAX, fsync_flags & IORING_FSYNC_DATASYNC); - io_fput(req); io_cqring_add_event(req->ctx, sqe->user_data, ret, 0); io_put_req(req); return 0; @@ -1220,7 +1152,6 @@ static int io_poll_remove(struct io_kiocb *req, const struct io_uring_sqe *sqe) static void io_poll_complete(struct io_kiocb *req, __poll_t mask) { io_cqring_add_event(req->ctx, req->user_data, mangle_poll(mask), 0); - io_fput(req); io_put_req(req); } @@ -1314,34 +1245,20 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe) struct io_poll_iocb *poll = &req->poll; struct io_ring_ctx *ctx = req->ctx; struct io_poll_table ipt; - unsigned flags; __poll_t mask; u16 events; - int fd; if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL)) return -EINVAL; if (sqe->addr || sqe->ioprio || sqe->off || sqe->len || sqe->buf_index) return -EINVAL; + if (!poll->file) + return -EBADF; INIT_WORK(&req->work, io_poll_complete_work); events = READ_ONCE(sqe->poll_events); poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP; - flags = READ_ONCE(sqe->flags); - fd = READ_ONCE(sqe->fd); - - if (flags & IOSQE_FIXED_FILE) { - if (unlikely(!ctx->user_files || fd >= ctx->nr_user_files)) - return -EBADF; - poll->file = ctx->user_files[fd]; - req->flags |= REQ_F_FIXED_FILE; - } else { - poll->file = fget(fd); - } - if (unlikely(!poll->file)) - return -EBADF; - poll->head = NULL; poll->woken = false; poll->canceled = false; @@ -1380,8 +1297,6 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe) out: if (unlikely(ipt.error)) { - if (!(flags & IOSQE_FIXED_FILE)) - fput(poll->file); /* * Drop one of our refs to this req, __io_submit_sqe() will * drop the other one since we're returning an error. @@ -1621,6 +1536,50 @@ static bool io_add_to_prev_work(struct async_list *list, struct io_kiocb *req) return ret; } +static bool io_op_needs_file(const struct io_uring_sqe *sqe) +{ + int op = READ_ONCE(sqe->opcode); + + switch (op) { + case IORING_OP_NOP: + case IORING_OP_POLL_REMOVE: + return false; + default: + return true; + } +} + +static int io_req_set_file(struct io_ring_ctx *ctx, const struct sqe_submit *s, + struct io_submit_state *state, struct io_kiocb *req) +{ + unsigned flags; + int fd; + + flags = READ_ONCE(s->sqe->flags); + fd = READ_ONCE(s->sqe->fd); + + if (!io_op_needs_file(s->sqe)) { + req->file = NULL; + return 0; + } + + if (flags & IOSQE_FIXED_FILE) { + if (unlikely(!ctx->user_files || + (unsigned) fd >= ctx->nr_user_files)) + return -EBADF; + req->file = ctx->user_files[fd]; + req->flags |= REQ_F_FIXED_FILE; + } else { + if (s->needs_fixed_file) + return -EBADF; + req->file = io_file_get(state, fd); + if (unlikely(!req->file)) + return -EBADF; + } + + return 0; +} + static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s, struct io_submit_state *state) { @@ -1635,6 +1594,10 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s, if (unlikely(!req)) return -EAGAIN; + ret = io_req_set_file(ctx, s, state, req); + if (unlikely(ret)) + goto out; + ret = __io_submit_sqe(ctx, req, s, true, state); if (ret == -EAGAIN) { struct io_uring_sqe *sqe_copy; @@ -1664,6 +1627,7 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s, } } +out: /* drop submission reference */ io_put_req(req); -- 2.7.4