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Date: Thu, 25 Apr 2024 14:52:42 +0200
From: Benjamin Tissoires <bentiss@kernel.org>
To: Dan Carpenter <dan.carpenter@linaro.org>
Cc: oe-kbuild@lists.linux.dev, Jiri Kosina <jikos@kernel.org>, 
	Benjamin Tissoires <benjamin.tissoires@redhat.com>, lkp@intel.com, oe-kbuild-all@lists.linux.dev, 
	linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 3/3] HID: bpf: lazy load the hid_tail_call entrypoint
Message-ID: <d2o5su7hxsnn3oarbowljss5fkmj2ttwiq4lf3g2putn7fc4it@uq2dui2tuxjk>
References: <20240419-hid_bpf_lazy_skel-v1-3-9210bcd4b61c@kernel.org>
 <74d0e9d1-7ac6-4f08-bab6-76c51e69cebf@moroto.mountain>
 <x7ffovagmqjazr6jhr6urkctcj7ozn6poakvjluorhzuxmyyg2@dxw7ucw3qc6z>
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In-Reply-To: <x7ffovagmqjazr6jhr6urkctcj7ozn6poakvjluorhzuxmyyg2@dxw7ucw3qc6z>

On Apr 24 2024, Benjamin Tissoires wrote:
> On Apr 23 2024, Dan Carpenter wrote:
> > Hi Benjamin,
> > 
> > kernel test robot noticed the following build warnings:
> > 
> > url:    https://github.com/intel-lab-lkp/linux/commits/Benjamin-Tissoires/HID-bpf-fix-a-comment-in-a-define/20240419-225110
> > base:   b912cf042072e12e93faa874265b30cc0aa521b9
> > patch link:    https://lore.kernel.org/r/20240419-hid_bpf_lazy_skel-v1-3-9210bcd4b61c%40kernel.org
> > patch subject: [PATCH 3/3] HID: bpf: lazy load the hid_tail_call entrypoint
> > config: i386-randconfig-141-20240423 (https://download.01.org/0day-ci/archive/20240423/202404231109.h2IRrMMD-lkp@intel.com/config)
> > compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > | Closes: https://lore.kernel.org/r/202404231109.h2IRrMMD-lkp@intel.com/
> > 
> > smatch warnings:
> > drivers/hid/bpf/hid_bpf_jmp_table.c:478 __hid_bpf_attach_prog() error: uninitialized symbol 'link'.
> > 
> > vim +/link +478 drivers/hid/bpf/hid_bpf_jmp_table.c
> > 
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  396  noinline int
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  397  __hid_bpf_attach_prog(struct hid_device *hdev, enum hid_bpf_prog_type prog_type,
> > 7cdd2108903a4e3 Benjamin Tissoires 2024-01-24  398  		      int prog_fd, struct bpf_prog *prog, __u32 flags)
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  399  {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  400  	struct bpf_link_primer link_primer;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  401  	struct hid_bpf_link *link;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  402  	struct hid_bpf_prog_entry *prog_entry;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  403  	int cnt, err = -EINVAL, prog_table_idx = -1;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  404  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  405  	mutex_lock(&hid_bpf_attach_lock);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  406  
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  407  	if (!jmp_table.map) {
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  408  		err = hid_bpf_preload_skel();
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  409  		WARN_ONCE(err, "error while preloading HID BPF dispatcher: %d", err);
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  410  		if (err)
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  411  			goto err_unlock;
> >                                                                         ^^^^^^^^^^^^^^^^
> > link isn't initialized.
> 
> Well spotted! Thanks
> I'll send a v2 soon.

FWIW, this patch prevents the proper unloading of the HID-BPF programs.
So not sure we'll want it as such just now.

Cheers,
Benjamin

> > 
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  412  	}
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19  413  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  414  	link = kzalloc(sizeof(*link), GFP_USER);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  415  	if (!link) {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  416  		err = -ENOMEM;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  417  		goto err_unlock;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  418  	}
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  419  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  420  	bpf_link_init(&link->link, BPF_LINK_TYPE_UNSPEC,
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  421  		      &hid_bpf_link_lops, prog);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  422  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  423  	/* do not attach too many programs to a given HID device */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  424  	cnt = hid_bpf_program_count(hdev, NULL, prog_type);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  425  	if (cnt < 0) {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  426  		err = cnt;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  427  		goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  428  	}
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  429  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  430  	if (cnt >= hid_bpf_max_programs(prog_type)) {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  431  		err = -E2BIG;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  432  		goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  433  	}
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  434  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  435  	prog_table_idx = hid_bpf_insert_prog(prog_fd, prog);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  436  	/* if the jmp table is full, abort */
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  437  	if (prog_table_idx < 0) {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  438  		err = prog_table_idx;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  439  		goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  440  	}
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  441  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  442  	if (flags & HID_BPF_FLAG_INSERT_HEAD) {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  443  		/* take the previous prog_entry slot */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  444  		jmp_table.tail = PREV(jmp_table.tail);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  445  		prog_entry = &jmp_table.entries[jmp_table.tail];
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  446  	} else {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  447  		/* take the next prog_entry slot */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  448  		prog_entry = &jmp_table.entries[jmp_table.head];
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  449  		jmp_table.head = NEXT(jmp_table.head);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  450  	}
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  451  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  452  	/* we steal the ref here */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  453  	prog_entry->prog = prog;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  454  	prog_entry->idx = prog_table_idx;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  455  	prog_entry->hdev = hdev;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  456  	prog_entry->type = prog_type;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  457  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  458  	/* finally store the index in the device list */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  459  	err = hid_bpf_populate_hdev(hdev, prog_type);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  460  	if (err) {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  461  		hid_bpf_release_prog_at(prog_table_idx);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  462  		goto err_unlock;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  463  	}
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  464  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  465  	link->hid_table_index = prog_table_idx;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  466  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  467  	err = bpf_link_prime(&link->link, &link_primer);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  468  	if (err)
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  469  		goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  470  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  471  	mutex_unlock(&hid_bpf_attach_lock);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  472  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  473  	return bpf_link_settle(&link_primer);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  474  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  475   err_unlock:
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  476  	mutex_unlock(&hid_bpf_attach_lock);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13  477  
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 @478  	kfree(link);
> >                                                               ^^^^
> > 
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  479  
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  480  	return err;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03  481  }
> > 
> > -- 
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
> >