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io_uring: fix files grab/cancel race
When one task is in io_uring_cancel_files() and another is doing io_prep_async_work() a race may happen. That's because after accounting a request inflight in first call to io_grab_identity() it still may fail and go to io_identity_cow(), which migh briefly keep dangling work.identity and not only. Grab files last, so io_prep_async_work() won't fail if it did get into ->inflight_list. note: the bug shouldn't exist after making io_uring_cancel_files() not poking into other tasks' requests. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -1313,22 +1313,6 @@ static bool io_grab_identity(struct io_kiocb *req)
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return false;
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req->work.flags |= IO_WQ_WORK_FSIZE;
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}
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if (!(req->work.flags & IO_WQ_WORK_FILES) &&
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(def->work_flags & IO_WQ_WORK_FILES) &&
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!(req->flags & REQ_F_NO_FILE_TABLE)) {
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if (id->files != current->files ||
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id->nsproxy != current->nsproxy)
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return false;
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atomic_inc(&id->files->count);
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get_nsproxy(id->nsproxy);
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req->flags |= REQ_F_INFLIGHT;
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spin_lock_irq(&ctx->inflight_lock);
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list_add(&req->inflight_entry, &ctx->inflight_list);
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spin_unlock_irq(&ctx->inflight_lock);
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req->work.flags |= IO_WQ_WORK_FILES;
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}
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#ifdef CONFIG_BLK_CGROUP
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if (!(req->work.flags & IO_WQ_WORK_BLKCG) &&
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(def->work_flags & IO_WQ_WORK_BLKCG)) {
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@ -1370,6 +1354,21 @@ static bool io_grab_identity(struct io_kiocb *req)
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}
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spin_unlock(¤t->fs->lock);
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}
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if (!(req->work.flags & IO_WQ_WORK_FILES) &&
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(def->work_flags & IO_WQ_WORK_FILES) &&
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!(req->flags & REQ_F_NO_FILE_TABLE)) {
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if (id->files != current->files ||
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id->nsproxy != current->nsproxy)
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return false;
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atomic_inc(&id->files->count);
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get_nsproxy(id->nsproxy);
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req->flags |= REQ_F_INFLIGHT;
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spin_lock_irq(&ctx->inflight_lock);
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list_add(&req->inflight_entry, &ctx->inflight_list);
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spin_unlock_irq(&ctx->inflight_lock);
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req->work.flags |= IO_WQ_WORK_FILES;
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}
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return true;
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}
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