CVE-2025-38263: In the Linux kernel, the following vulnerability has been resolved:  bcache: fix NULL pointer in cache_set_flush()  1. LINE#1794 - LINE#1887 is some codes about function of    bch_cache_set_alloc(). 2. LINE#2078 - LINE#2142 is some codes about function of    register_cache_set(). 3. register_cache_set() will call bch_cache_set_alloc() in LINE#2098.   1794 struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)  1795 {  ...  1860         if (!(c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL)) ||  1861             mempool_init_slab_pool(&c->search, 32, bch_search_cache) ||  1862             mempool_init_kmalloc_pool(&c->bio_meta, 2,  1863                                 sizeof(struct bbio) + sizeof(struct bio_vec) *  1864                                 bucket_pages(c)) ||  1865             mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size) ||  1866             bioset_init(&c->bio_split, 4, offsetof(struct bbio, bio),  1867                         BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER) ||  1868             !(c->uuids = alloc_bucket_pages(GFP_KERNEL, c)) ||  1869             !(c->moving_gc_wq = alloc_workqueue("bcache_gc",  1870                                                 WQ_MEM_RECLAIM, 0)) ||  1871             bch_journal_alloc(c) ||  1872             bch_btree_cache_alloc(c) ||  1873             bch_open_buckets_alloc(c) ||  1874             bch_bset_sort_state_init(&c->sort, ilog2(c->btree_pages)))  1875                 goto err;                       ^^^^^^^^  1876  ...  1883         return c;  1884 err:  1885         bch_cache_set_unregister(c);               ^^^^^^^^^^^^^^^^^^^^^^^^^^^  1886         return NULL;  1887 }  ...  2078 static const char *register_cache_set(struct cache *ca)  2079 {  ...  2098         c = bch_cache_set_alloc(&ca->sb);  2099         if (!c)  2100                 return err;                       ^^^^^^^^^^  ...  2128         ca->set = c;  2129         ca->set->cache[ca->sb.nr_this_dev] = ca;               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  ...  2138         return NULL;  2139 err:  2140         bch_cache_set_unregister(c);  2141         return err;  2142 }  (1) If LINE#1860 - LINE#1874 is true, then do 'goto err'(LINE#1875) and     call bch_cache_set_unregister()(LINE#1885). (2) As (1) return NULL(LINE#1886), LINE#2098 - LINE#2100 would return. (3) As (2) has returned, LINE#2128 - LINE#2129 would do *not* give the     value to c->cache[], it means that c->cache[] is NULL.  LINE#1624 - LINE#1665 is some codes about function of cache_set_flush(). As (1), in LINE#1885 call bch_cache_set_unregister() ---> bch_cache_set_stop()      ---> closure_queue()           -.-> cache_set_flush() (as below LINE#1624)   1624 static void cache_set_flush(struct closure *cl)  1625 {  ...  1654         for_each_cache(ca, c, i)  1655                 if (ca->alloc_thread)                           ^^  1656                         kthread_stop(ca->alloc_thread);  ...  1665 }  (4) In LINE#1655 ca is NULL(see (3)) in cache_set_flush() then the     kernel crash occurred as below: [  846.712887] bcache: register_cache() error drbd6: cannot allocate memory [  846.713242] bcache: register_bcache() error : failed to register device [  846.713336] bcache: cache_set_free() Cache set 2f84bdc1-498a-4f2f-98a7-01946bf54287 unregistered [  846.713768] BUG: unable to handle kernel NULL pointer dereference at 00000000000009f8 [  846.714790] PGD 0 P4D 0 [  846.715129] Oops: 0000 [#1] SMP PTI [  846.715472] CPU: 19 PID: 5057 Comm: kworker/19:16 Kdump: loaded Tainted: G           OE    --------- -  - 4.18.0-147.5.1.el8_1.5es.3.x86_64 #1 [  846.716082] Hardware name: ESPAN GI-25212/X11DPL-i, BIOS 2.1 06/15/2018 [  846.716451] Workqueue: events cache_set_flush [bcache] [  846.716808] RIP: 0010:cache_set_flush+0xc9/0x1b0 [bcache] [  846.717155] Code: 00 4c 89 a5 b0 03 00 00 48 8b 85 68 f6 ff ff a8 08 0f 84 88 00 00 00 31 db 66 83 bd 3c f7 ff ff 00 48 8b 85 48 ff ff ff 74 28 <48> 8b b8 f8 09 00 0 ---truncated---