bpf: Add missing map_delete_elem method to bloom filter map

Without it, kernel crashes in map_delete_elem(), as reported
by syzbot.

BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 72c97067 P4D 72c97067 PUD 1e20c067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 6518 Comm: syz-executor196 Not tainted 5.15.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90002bafcb8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 1ffff92000575f9f RCX: 0000000000000000
RDX: 1ffffffff1327aba RSI: 0000000000000000 RDI: ffff888025a30c00
RBP: ffffc90002baff08 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff818525d8 R11: 0000000000000000 R12: ffffffff8993d560
R13: ffff888025a30c00 R14: ffff888024bc0000 R15: 0000000000000000
FS:  0000555557491300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000070189000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 map_delete_elem kernel/bpf/syscall.c:1220 [inline]
 __sys_bpf+0x34f1/0x5ee0 kernel/bpf/syscall.c:4606
 __do_sys_bpf kernel/bpf/syscall.c:4719 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4717 [inline]
 __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4717
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]

Fixes: 9330986c ("bpf: Add bloom filter map implementation")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211031171353.4092388-1-eric.dumazet@gmail.com

kernel/bpf/bloom_filter.c

@@ -77,6 +77,11 @@ static int bloom_map_pop_elem(struct bpf_map *map, void *value)
 	return -EOPNOTSUPP;
 }
 
+static int bloom_map_delete_elem(struct bpf_map *map, void *value)
+{
+	return -EOPNOTSUPP;
+}
+
 static struct bpf_map *bloom_map_alloc(union bpf_attr *attr)
 {
 	u32 bitset_bytes, bitset_mask, nr_hash_funcs, nr_bits;
@@ -192,6 +197,7 @@ const struct bpf_map_ops bloom_filter_map_ops = {
 	.map_pop_elem = bloom_map_pop_elem,
 	.map_lookup_elem = bloom_map_lookup_elem,
 	.map_update_elem = bloom_map_update_elem,
+	.map_delete_elem = bloom_map_delete_elem,
 	.map_check_btf = bloom_map_check_btf,
 	.map_btf_name = "bpf_bloom_filter",
 	.map_btf_id = &bpf_bloom_map_btf_id,