Patch "tcp: Fix refcnt handling in __inet_hash_connect()." has been added to the 6.8-stable tree

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This is a note to let you know that I've just added the patch titled

    tcp: Fix refcnt handling in __inet_hash_connect().

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-fix-refcnt-handling-in-__inet_hash_connect.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5e36fdd170273823d3eae8a2a8580b99b71bb930
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Fri Mar 8 12:16:23 2024 -0800

    tcp: Fix refcnt handling in __inet_hash_connect().
    
    [ Upstream commit 04d9d1fc428ac9f581d55118d67e0cb546701feb ]
    
    syzbot reported a warning in sk_nulls_del_node_init_rcu().
    
    The commit 66b60b0c8c4a ("dccp/tcp: Unhash sk from ehash for tb2 alloc
    failure after check_estalblished().") tried to fix an issue that an
    unconnected socket occupies an ehash entry when bhash2 allocation fails.
    
    In such a case, we need to revert changes done by check_established(),
    which does not hold refcnt when inserting socket into ehash.
    
    So, to revert the change, we need to __sk_nulls_add_node_rcu() instead
    of sk_nulls_add_node_rcu().
    
    Otherwise, sock_put() will cause refcnt underflow and leak the socket.
    
    [0]:
    WARNING: CPU: 0 PID: 23948 at include/net/sock.h:799 sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799
    Modules linked in:
    CPU: 0 PID: 23948 Comm: syz-executor.2 Not tainted 6.8.0-rc6-syzkaller-00159-gc055fc00c07b #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
    RIP: 0010:sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799
    Code: e8 7f 71 c6 f7 83 fb 02 7c 25 e8 35 6d c6 f7 4d 85 f6 0f 95 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 1b 6d c6 f7 90 <0f> 0b 90 eb b2 e8 10 6d c6 f7 4c 89 e7 be 04 00 00 00 e8 63 e7 d2
    RSP: 0018:ffffc900032d7848 EFLAGS: 00010246
    RAX: ffffffff89cd0035 RBX: 0000000000000001 RCX: 0000000000040000
    RDX: ffffc90004de1000 RSI: 000000000003ffff RDI: 0000000000040000
    RBP: 1ffff1100439ac26 R08: ffffffff89ccffe3 R09: 1ffff1100439ac28
    R10: dffffc0000000000 R11: ffffed100439ac29 R12: ffff888021cd6140
    R13: dffffc0000000000 R14: ffff88802a9bf5c0 R15: ffff888021cd6130
    FS:  00007f3b823f16c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007f3b823f0ff8 CR3: 000000004674a000 CR4: 00000000003506f0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     <TASK>
     __inet_hash_connect+0x140f/0x20b0 net/ipv4/inet_hashtables.c:1139
     dccp_v6_connect+0xcb9/0x1480 net/dccp/ipv6.c:956
     __inet_stream_connect+0x262/0xf30 net/ipv4/af_inet.c:678
     inet_stream_connect+0x65/0xa0 net/ipv4/af_inet.c:749
     __sys_connect_file net/socket.c:2048 [inline]
     __sys_connect+0x2df/0x310 net/socket.c:2065
     __do_sys_connect net/socket.c:2075 [inline]
     __se_sys_connect net/socket.c:2072 [inline]
     __x64_sys_connect+0x7a/0x90 net/socket.c:2072
     do_syscall_64+0xf9/0x240
     entry_SYSCALL_64_after_hwframe+0x6f/0x77
    RIP: 0033:0x7f3b8167dda9
    Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
    RSP: 002b:00007f3b823f10c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
    RAX: ffffffffffffffda RBX: 00007f3b817abf80 RCX: 00007f3b8167dda9
    RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003
    RBP: 00007f3b823f1120 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
    R13: 000000000000000b R14: 00007f3b817abf80 R15: 00007ffd3beb57b8
     </TASK>
    
    Reported-by: syzbot+12c506c1aae251e70449@xxxxxxxxxxxxxxxxxxxxxxxxx
    Closes: https://syzkaller.appspot.com/bug?extid=12c506c1aae251e70449
    Fixes: 66b60b0c8c4a ("dccp/tcp: Unhash sk from ehash for tb2 alloc failure after check_estalblished().")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240308201623.65448-1-kuniyu@xxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 308ff34002ea6..4e470f18487f6 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -1136,7 +1136,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 		sock_prot_inuse_add(net, sk->sk_prot, -1);
 
 		spin_lock(lock);
-		sk_nulls_del_node_init_rcu(sk);
+		__sk_nulls_del_node_init_rcu(sk);
 		spin_unlock(lock);
 
 		sk->sk_hash = 0;




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