• Hawkins Jiawei's avatar
    net: fix refcount bug in sk_psock_get (2) · 2a013372
    Hawkins Jiawei authored
    Syzkaller reports refcount bug as follows:
    ------------[ cut here ]------------
    refcount_t: saturated; leaking memory.
    WARNING: CPU: 1 PID: 3605 at lib/refcount.c:19 refcount_warn_saturate+0xf4/0x1e0 lib/refcount.c:19
    Modules linked in:
    CPU: 1 PID: 3605 Comm: syz-executor208 Not tainted 5.18.0-syzkaller-03023-g7e062cda #0
     <TASK>
     __refcount_add_not_zero include/linux/refcount.h:163 [inline]
     __refcount_inc_not_zero include/linux/refcount.h:227 [inline]
     refcount_inc_not_zero include/linux/refcount.h:245 [inline]
     sk_psock_get+0x3bc/0x410 include/linux/skmsg.h:439
     tls_data_ready+0x6d/0x1b0 net/tls/tls_sw.c:2091
     tcp_data_ready+0x106/0x520 net/ipv4/tcp_input.c:4983
     tcp_data_queue+0x25f2/0x4c90 net/ipv4/tcp_input.c:5057
     tcp_rcv_state_process+0x1774/0x4e80 net/ipv4/tcp_input.c:6659
     tcp_v4_do_rcv+0x339/0x980 net/ipv4/tcp_ipv4.c:1682
     sk_backlog_rcv include/net/sock.h:1061 [inline]
     __release_sock+0x134/0x3b0 net/core/sock.c:2849
     release_sock+0x54/0x1b0 net/core/sock.c:3404
     inet_shutdown+0x1e0/0x430 net/ipv4/af_inet.c:909
     __sys_shutdown_sock net/socket.c:2331 [inline]
     __sys_shutdown_sock net/socket.c:2325 [inline]
     __sys_shutdown+0xf1/0x1b0 net/socket.c:2343
     __do_sys_shutdown net/socket.c:2351 [inline]
     __se_sys_shutdown net/socket.c:2349 [inline]
     __x64_sys_shutdown+0x50/0x70 net/socket.c:2349
     do_syscall_x64 arch/x86/entry/common.c:50 [inline]
     do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
     entry_SYSCALL_64_after_hwframe+0x46/0xb0
     </TASK>
    
    During SMC fallback process in connect syscall, kernel will
    replaces TCP with SMC. In order to forward wakeup
    smc socket waitqueue after fallback, kernel will sets
    clcsk->sk_user_data to origin smc socket in
    smc_fback_replace_callbacks().
    
    Later, in shutdown syscall, kernel will calls
    sk_psock_get(), which treats the clcsk->sk_user_data
    as psock type, triggering the refcnt warning.
    
    So, the root cause is that smc and psock, both will use
    sk_user_data field. So they will mismatch this field
    easily.
    
    This patch solves it by using another bit(defined as
    SK_USER_DATA_PSOCK) in PTRMASK, to mark whether
    sk_user_data points to a psock object or not.
    This patch depends on a PTRMASK introduced in commit f1ff5ce2
    ("net, sk_msg: Clear sk_user_data pointer on clone if tagged").
    
    For there will possibly be more flags in the sk_user_data field,
    this patch also refactor sk_user_data flags code to be more generic
    to improve its maintainability.
    
    Reported-and-tested-by: syzbot+5f26f85569bd179c18ce@syzkaller.appspotmail.com
    Suggested-by: default avatarJakub Kicinski <kuba@kernel.org>
    Acked-by: default avatarWen Gu <guwen@linux.alibaba.com>
    Signed-off-by: default avatarHawkins Jiawei <yin31149@gmail.com>
    Reviewed-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
    Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    2a013372
skmsg.c 28.3 KB