drivers/block/drbd/drbd_worker.c:588 make_resync_request() warn: variable dereferenced before check 'peer_device' (see line 587)

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   ce36c8b149873b50f2a4b9818eb3dcdd74ddd5a3
commit: 0d11f3cf279c5ad20a41f29242f170ba3c02f2da drbd: Pass a peer device to the resync and online verify functions
config: x86_64-randconfig-161-20231003 (https://download.01.org/0day-ci/archive/20231003/202310030935.6F0FaCJy-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231003/202310030935.6F0FaCJy-lkp@xxxxxxxxx/reproduce)

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@xxxxxxxxx>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202310030935.6F0FaCJy-lkp@xxxxxxxxx/

smatch warnings:
drivers/block/drbd/drbd_worker.c:588 make_resync_request() warn: variable dereferenced before check 'peer_device' (see line 587)

vim +/peer_device +588 drivers/block/drbd/drbd_worker.c

0d11f3cf279c5a Christoph Böhmwalder 2023-03-30  585  static int make_resync_request(struct drbd_peer_device *const peer_device, int cancel)
b411b3637fa71f Philipp Reisner      2009-09-25  586  {
0d11f3cf279c5a Christoph Böhmwalder 2023-03-30 @587  	struct drbd_device *const device = peer_device->device;
                                                                                           ^^^^^^^^^^^^^^^^^^^^
Dereference

44a4d551846b8c Lars Ellenberg       2013-11-22 @588  	struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
                                                                                                   ^^^^^^^^^^^
Checked too late.  The zero day bot sent this warning earlier and I try
not to resend warnings but no one responded to the first one.  The
peer_device pointer comes from a list_first_entry_or_null() so that
suggests it can be NULL.

b411b3637fa71f Philipp Reisner      2009-09-25  589  	unsigned long bit;
b411b3637fa71f Philipp Reisner      2009-09-25  590  	sector_t sector;
155bd9d1abd604 Christoph Hellwig    2020-09-25  591  	const sector_t capacity = get_capacity(device->vdisk);
1816a2b47afae8 Lars Ellenberg       2010-11-11  592  	int max_bio_size;
e65f440d474d7d Lars Ellenberg       2010-11-05  593  	int number, rollback_i, size;
506afb6248af57 Lars Ellenberg       2014-01-31  594  	int align, requeue = 0;
0f0601f4ea2f53 Lars Ellenberg       2010-08-11  595  	int i = 0;
92d94ae66aebda Philipp Reisner      2016-06-14  596  	int discard_granularity = 0;
b411b3637fa71f Philipp Reisner      2009-09-25  597  
b411b3637fa71f Philipp Reisner      2009-09-25  598  	if (unlikely(cancel))
99920dc5c5fe52 Andreas Gruenbacher  2011-03-16  599  		return 0;

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