alg_memory_allocated does not seem to be really used.

alg_proto does have a .memory_allocated field, but no
corresponding .sysctl_mem.

This means sk_has_account() returns true, but all sk_prot_mem_limits()
users will trigger a NULL dereference [1].

THis was not a problem until SO_RESERVE_MEM addition.

general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 1 PID: 3591 Comm: syz-executor153 Not tainted 5.17.0-rc3-syzkaller-00316-gb81b1829 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:sk_prot_mem_limits include/net/sock.h:1523 [inline]
RIP: 0010:sock_reserve_memory+0x1d7/0x330 net/core/sock.c:1000
Code: 08 00 74 08 48 89 ef e8 27 20 bb f9 4c 03 7c 24 10 48 8b 6d 00 48 83 c5 08 48 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 ef e8 fb 1f bb f9 48 8b 6d 00 4c 89 ff 48
RSP: 0018:ffffc90001f1fb68 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff88814aabc000 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffff90e18120
RBP: 0000000000000008 R08: dffffc0000000000 R09: fffffbfff21c3025
R10: fffffbfff21c3025 R11: 0000000000000000 R12: ffffffff8d109840
R13: 0000000000001002 R14: 0000000000000001 R15: 0000000000000001
FS:  0000555556e08300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc74416f130 CR3: 0000000073d9e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 sock_setsockopt+0x14a9/0x3a30 net/core/sock.c:1446
 __sys_setsockopt+0x5af/0x980 net/socket.c:2176
 __do_sys_setsockopt net/socket.c:2191 [inline]
 __se_sys_setsockopt net/socket.c:2188 [inline]
 __x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2188
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fc7440fddc9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe98f07968 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fc7440fddc9
RDX: 0000000000000049 RSI: 0000000000000001 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000004 R09: 00007ffe98f07990
R10: 0000000020000000 R11: 0000000000000246 R12: 00007ffe98f0798c
R13: 00007ffe98f079a0 R14: 00007ffe98f079e0 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:sk_prot_mem_limits include/net/sock.h:1523 [inline]
RIP: 0010:sock_reserve_memory+0x1d7/0x330 net/core/sock.c:1000
Code: 08 00 74 08 48 89 ef e8 27 20 bb f9 4c 03 7c 24 10 48 8b 6d 00 48 83 c5 08 48 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 ef e8 fb 1f bb f9 48 8b 6d 00 4c 89 ff 48
RSP: 0018:ffffc90001f1fb68 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff88814aabc000 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffff90e18120
RBP: 0000000000000008 R08: dffffc0000000000 R09: fffffbfff21c3025
R10: fffffbfff21c3025 R11: 0000000000000000 R12: ffffffff8d109840
R13: 0000000000001002 R14: 0000000000000001 R15: 0000000000000001
FS:  0000555556e08300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc74416f130 CR3: 0000000073d9e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

Fixes: 2bb2f5fb ("net: add new socket option SO_RESERVE_MEM")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>