| Message ID | 20241212102000.2148788-1-ivanov.mikhail1@huawei-partners.com (mailing list archive) |
|---|---|
| State | Under Review |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | selinux: Read sk->sk_family once in selinux_socket_bind() | expand |
This looks good be there are other places using sk->sk_family that should also be fixed. On Thu, Dec 12, 2024 at 06:20:00PM +0800, Mikhail Ivanov wrote: > selinux_socket_bind() is called without holding the socket lock. > > Use READ_ONCE() to safely read sk->sk_family for IPv6 socket in case > of lockless transformation to IPv4 socket via IPV6_ADDRFORM [1]. > > [1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@google.com/ > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> > --- > security/selinux/hooks.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 5e5f3398f39d..b7adff2cf5f6 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -4715,8 +4715,10 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in > if (err) > goto out; > > + /* IPV6_ADDRFORM can change sk->sk_family under us. */ > + family = READ_ONCE(sk->sk_family); > + > /* If PF_INET or PF_INET6, check name_bind permission for the port. */ > - family = sk->sk_family; > if (family == PF_INET || family == PF_INET6) { > char *addrp; > struct common_audit_data ad; > > base-commit: 034294fbfdf0ded4f931f9503d2ca5bbf8b9aebd > -- > 2.34.1 > >
On 12/12/2024 8:50 PM, Mickaël Salaün wrote: > This looks good be there are other places using sk->sk_family that > should also be fixed. Thanks for checking this! For selinux this should be enough, I haven't found any other places where sk->sk_family could be read from an IPv6 socket without locking. I also would like to prepare such fix for other LSMs (apparmor, smack, tomoyo) (in separate patches). > > On Thu, Dec 12, 2024 at 06:20:00PM +0800, Mikhail Ivanov wrote: >> selinux_socket_bind() is called without holding the socket lock. >> >> Use READ_ONCE() to safely read sk->sk_family for IPv6 socket in case >> of lockless transformation to IPv4 socket via IPV6_ADDRFORM [1]. >> >> [1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@google.com/ >> >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> >> --- >> security/selinux/hooks.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c >> index 5e5f3398f39d..b7adff2cf5f6 100644 >> --- a/security/selinux/hooks.c >> +++ b/security/selinux/hooks.c >> @@ -4715,8 +4715,10 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in >> if (err) >> goto out; >> >> + /* IPV6_ADDRFORM can change sk->sk_family under us. */ >> + family = READ_ONCE(sk->sk_family); >> + >> /* If PF_INET or PF_INET6, check name_bind permission for the port. */ >> - family = sk->sk_family; >> if (family == PF_INET || family == PF_INET6) { >> char *addrp; >> struct common_audit_data ad; >> >> base-commit: 034294fbfdf0ded4f931f9503d2ca5bbf8b9aebd >> -- >> 2.34.1 >> >>
On Fri, Dec 13, 2024 at 5:57 AM Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> wrote: > > On 12/12/2024 8:50 PM, Mickaël Salaün wrote: > > This looks good be there are other places using sk->sk_family that > > should also be fixed. > > Thanks for checking this! > > For selinux this should be enough, I haven't found any other places > where sk->sk_family could be read from an IPv6 socket without locking. > > I also would like to prepare such fix for other LSMs (apparmor, smack, > tomoyo) (in separate patches). I'm wondering about the implications for SELinux beyond just sk->sk_family access, e.g. SELinux maps the (family, type, protocol) triple to a security class at socket creation time via socket_type_to_security_class() and caches the security class in the inode_security_struct and sk_security_struct for later use. > > > > > On Thu, Dec 12, 2024 at 06:20:00PM +0800, Mikhail Ivanov wrote: > >> selinux_socket_bind() is called without holding the socket lock. > >> > >> Use READ_ONCE() to safely read sk->sk_family for IPv6 socket in case > >> of lockless transformation to IPv4 socket via IPV6_ADDRFORM [1]. > >> > >> [1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@google.com/ > >> > >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > >> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> > >> --- > >> security/selinux/hooks.c | 4 +++- > >> 1 file changed, 3 insertions(+), 1 deletion(-) > >> > >> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > >> index 5e5f3398f39d..b7adff2cf5f6 100644 > >> --- a/security/selinux/hooks.c > >> +++ b/security/selinux/hooks.c > >> @@ -4715,8 +4715,10 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in > >> if (err) > >> goto out; > >> > >> + /* IPV6_ADDRFORM can change sk->sk_family under us. */ > >> + family = READ_ONCE(sk->sk_family); > >> + > >> /* If PF_INET or PF_INET6, check name_bind permission for the port. */ > >> - family = sk->sk_family; > >> if (family == PF_INET || family == PF_INET6) { > >> char *addrp; > >> struct common_audit_data ad; > >> > >> base-commit: 034294fbfdf0ded4f931f9503d2ca5bbf8b9aebd > >> -- > >> 2.34.1 > >> > >>
On 12/13/2024 6:46 PM, Stephen Smalley wrote: > On Fri, Dec 13, 2024 at 5:57 AM Mikhail Ivanov > <ivanov.mikhail1@huawei-partners.com> wrote: >> >> On 12/12/2024 8:50 PM, Mickaël Salaün wrote: >>> This looks good be there are other places using sk->sk_family that >>> should also be fixed. >> >> Thanks for checking this! >> >> For selinux this should be enough, I haven't found any other places >> where sk->sk_family could be read from an IPv6 socket without locking. >> >> I also would like to prepare such fix for other LSMs (apparmor, smack, >> tomoyo) (in separate patches). > > I'm wondering about the implications for SELinux beyond just > sk->sk_family access, e.g. SELinux maps the (family, type, protocol) > triple to a security class at socket creation time via > socket_type_to_security_class() and caches the security class in the > inode_security_struct and sk_security_struct for later use. IPv6 and IPv4 TCP sockets are mapped to the same SECCLASS_TCP_SOCKET security class. AFAICS there is no other places that can be affected by the IPV6_ADDFORM transformation. > >> >>> >>> On Thu, Dec 12, 2024 at 06:20:00PM +0800, Mikhail Ivanov wrote: >>>> selinux_socket_bind() is called without holding the socket lock. >>>> >>>> Use READ_ONCE() to safely read sk->sk_family for IPv6 socket in case >>>> of lockless transformation to IPv4 socket via IPV6_ADDRFORM [1]. >>>> >>>> [1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@google.com/ >>>> >>>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >>>> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> >>>> --- >>>> security/selinux/hooks.c | 4 +++- >>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c >>>> index 5e5f3398f39d..b7adff2cf5f6 100644 >>>> --- a/security/selinux/hooks.c >>>> +++ b/security/selinux/hooks.c >>>> @@ -4715,8 +4715,10 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in >>>> if (err) >>>> goto out; >>>> >>>> + /* IPV6_ADDRFORM can change sk->sk_family under us. */ >>>> + family = READ_ONCE(sk->sk_family); >>>> + >>>> /* If PF_INET or PF_INET6, check name_bind permission for the port. */ >>>> - family = sk->sk_family; >>>> if (family == PF_INET || family == PF_INET6) { >>>> char *addrp; >>>> struct common_audit_data ad; >>>> >>>> base-commit: 034294fbfdf0ded4f931f9503d2ca5bbf8b9aebd >>>> -- >>>> 2.34.1 >>>> >>>>
On Fri, Dec 13, 2024 at 11:40 AM Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> wrote: > > On 12/13/2024 6:46 PM, Stephen Smalley wrote: > > On Fri, Dec 13, 2024 at 5:57 AM Mikhail Ivanov > > <ivanov.mikhail1@huawei-partners.com> wrote: > >> > >> On 12/12/2024 8:50 PM, Mickaël Salaün wrote: > >>> This looks good be there are other places using sk->sk_family that > >>> should also be fixed. > >> > >> Thanks for checking this! > >> > >> For selinux this should be enough, I haven't found any other places > >> where sk->sk_family could be read from an IPv6 socket without locking. > >> > >> I also would like to prepare such fix for other LSMs (apparmor, smack, > >> tomoyo) (in separate patches). > > > > I'm wondering about the implications for SELinux beyond just > > sk->sk_family access, e.g. SELinux maps the (family, type, protocol) > > triple to a security class at socket creation time via > > socket_type_to_security_class() and caches the security class in the > > inode_security_struct and sk_security_struct for later use. > > IPv6 and IPv4 TCP sockets are mapped to the same SECCLASS_TCP_SOCKET > security class. AFAICS there is no other places that can be affected by > the IPV6_ADDFORM transformation. Great, thank you for checking!
On Fri, Dec 13, 2024 at 11:40 AM Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> wrote: > On 12/13/2024 6:46 PM, Stephen Smalley wrote: > > On Fri, Dec 13, 2024 at 5:57 AM Mikhail Ivanov > > <ivanov.mikhail1@huawei-partners.com> wrote: > >> > >> On 12/12/2024 8:50 PM, Mickaël Salaün wrote: > >>> This looks good be there are other places using sk->sk_family that > >>> should also be fixed. > >> > >> Thanks for checking this! > >> > >> For selinux this should be enough, I haven't found any other places > >> where sk->sk_family could be read from an IPv6 socket without locking. > >> > >> I also would like to prepare such fix for other LSMs (apparmor, smack, > >> tomoyo) (in separate patches). > > > > I'm wondering about the implications for SELinux beyond just > > sk->sk_family access, e.g. SELinux maps the (family, type, protocol) > > triple to a security class at socket creation time via > > socket_type_to_security_class() and caches the security class in the > > inode_security_struct and sk_security_struct for later use. > > IPv6 and IPv4 TCP sockets are mapped to the same SECCLASS_TCP_SOCKET > security class. AFAICS there is no other places that can be affected by > the IPV6_ADDFORM transformation. Yes, thankfully we don't really encode the IP address family in any of the SELinux object classes so that shouldn't be an issue. I also don't think we have to worry about the per-packet labeling protocols as it's too late in the communication to change the socket's associated packet labeling, it's either working or it isn't; we should handle the mapped IPv4 address already. I am a little concerned about bind being the only place where we have to worry about accessing sk_family while the socket isn't locked. As an example, I'm a little concerned about the netfilter code paths; I haven't chased them down, but my guess is that the associated socket/sock isn't locked in those cases (in the relevant output and postroute cases, forward should be a non-issue). How bad is the performance impact of READ_ONCE()? In other words, how stupid would it be to simply do all of our sock->sk_family lookups using READ_ONCE()?
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 5e5f3398f39d..b7adff2cf5f6 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -4715,8 +4715,10 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in if (err) goto out; + /* IPV6_ADDRFORM can change sk->sk_family under us. */ + family = READ_ONCE(sk->sk_family); + /* If PF_INET or PF_INET6, check name_bind permission for the port. */ - family = sk->sk_family; if (family == PF_INET || family == PF_INET6) { char *addrp; struct common_audit_data ad;
selinux_socket_bind() is called without holding the socket lock. Use READ_ONCE() to safely read sk->sk_family for IPv6 socket in case of lockless transformation to IPv4 socket via IPV6_ADDRFORM [1]. [1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@google.com/ Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> --- security/selinux/hooks.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) base-commit: 034294fbfdf0ded4f931f9503d2ca5bbf8b9aebd