drivers/md/bcache/btree.c:1511 btree_gc_rewrite_node() error: 'n' dereferencing possible ERR_PTR()

[Dan Carpenter]

Hi Zheng,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   77fa2fbe87fc605c4bfa87dff87be9bfded0e9a3
commit: 028ddcac477b691dd9205c92f991cc15259d033e bcache: Remove unnecessary NULL point check in node allocations
config: x86_64-randconfig-161-20231102 (https://download.01.org/0day-ci/archive/20231106/202311060857.2jHVe0uk-lkp@xxxxxxxxx/config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce: (https://download.01.org/0day-ci/archive/20231106/202311060857.2jHVe0uk-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/202311060857.2jHVe0uk-lkp@xxxxxxxxx/

New smatch warnings:
drivers/md/bcache/btree.c:1511 btree_gc_rewrite_node() error: 'n' dereferencing possible ERR_PTR()

Old smatch warnings:
drivers/md/bcache/btree.c:1527 btree_gc_rewrite_node() error: 'n' dereferencing possible ERR_PTR()

vim +/n +1511 drivers/md/bcache/btree.c

0a63b66db566cf Kent Overstreet 2014-03-17  1497  static int btree_gc_rewrite_node(struct btree *b, struct btree_op *op,
0a63b66db566cf Kent Overstreet 2014-03-17  1498  				 struct btree *replace)
0a63b66db566cf Kent Overstreet 2014-03-17  1499  {
0a63b66db566cf Kent Overstreet 2014-03-17  1500  	struct keylist keys;
0a63b66db566cf Kent Overstreet 2014-03-17  1501  	struct btree *n;
0a63b66db566cf Kent Overstreet 2014-03-17  1502  
0a63b66db566cf Kent Overstreet 2014-03-17  1503  	if (btree_check_reserve(b, NULL))
0a63b66db566cf Kent Overstreet 2014-03-17  1504  		return 0;
0a63b66db566cf Kent Overstreet 2014-03-17  1505  
0a63b66db566cf Kent Overstreet 2014-03-17  1506  	n = btree_node_alloc_replacement(replace, NULL);

Needs some error handling.  I don't know why the zero day bot is
sending repeat warnings today but this one is still worth fixing.
I guess the zero day bot sent the previous warning to the wrong people
last time.

https://lore.kernel.org/all/bab6966d-3f96-44a0-b666-ddf976179eab@kadam.mountain/

0a63b66db566cf Kent Overstreet 2014-03-17  1507  
0a63b66db566cf Kent Overstreet 2014-03-17  1508  	/* recheck reserve after allocating replacement node */
0a63b66db566cf Kent Overstreet 2014-03-17  1509  	if (btree_check_reserve(b, NULL)) {
0a63b66db566cf Kent Overstreet 2014-03-17  1510  		btree_node_free(n);
0a63b66db566cf Kent Overstreet 2014-03-17 @1511  		rw_unlock(true, n);
0a63b66db566cf Kent Overstreet 2014-03-17  1512  		return 0;
0a63b66db566cf Kent Overstreet 2014-03-17  1513  	}
0a63b66db566cf Kent Overstreet 2014-03-17  1514  
0a63b66db566cf Kent Overstreet 2014-03-17  1515  	bch_btree_node_write_sync(n);
0a63b66db566cf Kent Overstreet 2014-03-17  1516  
0a63b66db566cf Kent Overstreet 2014-03-17  1517  	bch_keylist_init(&keys);
0a63b66db566cf Kent Overstreet 2014-03-17  1518  	bch_keylist_add(&keys, &n->key);
0a63b66db566cf Kent Overstreet 2014-03-17  1519  
0a63b66db566cf Kent Overstreet 2014-03-17  1520  	make_btree_freeing_key(replace, keys.top);
0a63b66db566cf Kent Overstreet 2014-03-17  1521  	bch_keylist_push(&keys);
0a63b66db566cf Kent Overstreet 2014-03-17  1522  
0a63b66db566cf Kent Overstreet 2014-03-17  1523  	bch_btree_insert_node(b, op, &keys, NULL, NULL);
0a63b66db566cf Kent Overstreet 2014-03-17  1524  	BUG_ON(!bch_keylist_empty(&keys));
0a63b66db566cf Kent Overstreet 2014-03-17  1525  
0a63b66db566cf Kent Overstreet 2014-03-17  1526  	btree_node_free(replace);
0a63b66db566cf Kent Overstreet 2014-03-17  1527  	rw_unlock(true, n);
0a63b66db566cf Kent Overstreet 2014-03-17  1528  
0a63b66db566cf Kent Overstreet 2014-03-17  1529  	/* Invalidated our iterator */
0a63b66db566cf Kent Overstreet 2014-03-17  1530  	return -EINTR;
0a63b66db566cf Kent Overstreet 2014-03-17  1531  }

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