• Mikulas Patocka's avatar
    tun: fix a crash bug and a memory leak · b09e786b
    Mikulas Patocka authored
    This patch fixes a crash
    tun_chr_close -> netdev_run_todo -> tun_free_netdev -> sk_release_kernel ->
    sock_release -> iput(SOCK_INODE(sock))
    introduced by commit 1ab5ecb9
    
    The problem is that this socket is embedded in struct tun_struct, it has
    no inode, iput is called on invalid inode, which modifies invalid memory
    and optionally causes a crash.
    
    sock_release also decrements sockets_in_use, this causes a bug that
    "sockets: used" field in /proc/*/net/sockstat keeps on decreasing when
    creating and closing tun devices.
    
    This patch introduces a flag SOCK_EXTERNALLY_ALLOCATED that instructs
    sock_release to not free the inode and not decrement sockets_in_use,
    fixing both memory corruption and sockets_in_use underflow.
    
    It should be backported to 3.3 an 3.4 stabke.
    Signed-off-by: default avatarMikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
    Cc: stable@kernel.org
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    b09e786b
tun.c 38.5 KB