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    SubjectRe: [PATCH - BUGFIX] Smack: Check for 'struct socket' with NULL sk

    --- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:

    > On Mon, Feb 11, 2008 at 07:26:02PM +0100, Joerg Platte wrote:
    > > Hi,
    > >
    > > when booting linux 2.6.25-rc1 I get the following error:
    > >
    > > BUG: unable to handle kernel NULL pointer dereference at 00000138
    > > IP: [<c01aa59e>] smack_netlabel+0x13/0xc8
    > > *pde = 00000000
    > > Oops: 0000 [#1] PREEMPT
    > > Modules linked in: nfsd
    > [...]
    > > Call Trace:
    > > [<c01aacf8>] ? new_inode_smack+0x39/0x3f
    > > [<c01aad52>] ? smack_inode_alloc_security+0x16/0x27
    > > [<c01a7510>] ? security_inode_alloc+0x19/0x1b
    > > [<c01aa665>] ? smack_socket_post_create+0x12/0x18
    > > [<c01a7a06>] ? security_socket_post_create+0x16/0x1b
    > > [<c02116ce>] ? sock_create_lite+0x44/0x64
    > > [<c0211712>] ? kernel_accept+0x24/0x5f
    >
    > Hi Joerg,
    >
    > There's a small problem with smack and NFS. A similar report was also
    > sent here: http://lkml.org/lkml/2007/10/27/85
    >
    > Could you please check below patch ? I think it should fix your problem.
    >
    > I've also added similar checks in inode_{get/set}security(). Cheating
    > from SELinux post_create_socket(), it does the same. Casey, Thoughts ?
    >
    > Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
    Acked-by: Casey Schaufler <casey@schuafler-ca.com>

    This looks like the right sort of thing to do. I would like
    to see it in. If you would like Ahmed, please submit with my
    Acknowlegement. Thank you for the work on this.

    > ---
    > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
    > index 1c11e42..eb04278 100644
    > --- a/security/smack/smack_lsm.c
    > +++ b/security/smack/smack_lsm.c
    > @@ -701,7 +701,7 @@ static int smack_inode_getsecurity(const struct inode
    > *inode,
    > return -EOPNOTSUPP;
    >
    > sock = SOCKET_I(ip);
    > - if (sock == NULL)
    > + if (sock == NULL || sock->sk == NULL)
    > return -EOPNOTSUPP;
    >
    > ssp = sock->sk->sk_security;
    > @@ -1280,10 +1280,12 @@ static void smack_to_secattr(char *smack, struct
    > netlbl_lsm_secattr *nlsp)
    > */
    > static int smack_netlabel(struct sock *sk)
    > {
    > - struct socket_smack *ssp = sk->sk_security;
    > + struct socket_smack *ssp;
    > struct netlbl_lsm_secattr secattr;
    > int rc = 0;
    >
    > + BUG_ON(sk == NULL);
    > + ssp = sk->sk_security;
    > netlbl_secattr_init(&secattr);
    > smack_to_secattr(ssp->smk_out, &secattr);
    > if (secattr.flags != NETLBL_SECATTR_NONE)
    > @@ -1331,7 +1333,7 @@ static int smack_inode_setsecurity(struct inode *inode,
    > const char *name,
    > return -EOPNOTSUPP;
    >
    > sock = SOCKET_I(inode);
    > - if (sock == NULL)
    > + if (sock == NULL || sock->sk == NULL)
    > return -EOPNOTSUPP;
    >
    > ssp = sock->sk->sk_security;
    > @@ -1362,7 +1364,7 @@ static int smack_inode_setsecurity(struct inode *inode,
    > const char *name,
    > static int smack_socket_post_create(struct socket *sock, int family,
    > int type, int protocol, int kern)
    > {
    > - if (family != PF_INET)
    > + if (family != PF_INET || sock->sk == NULL)
    > return 0;
    > /*
    > * Set the outbound netlbl.
    > --
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    > Please read the FAQ at http://www.tux.org/lkml/
    >
    >
    >


    Casey Schaufler
    casey@schaufler-ca.com


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