[3/3] Compare namespaces when comparing addresses in auth_unix cache.
diff mbox

Message ID 4D9431B3.2070305@parallels.com
State New, archived
Headers show

Commit Message

Rob Landley March 31, 2011, 7:48 a.m. UTC
None

Comments

Serge E. Hallyn April 5, 2011, 3:46 a.m. UTC | #1
Quoting Rob Landley (rlandley@parallels.com):
> From: Rob Landley <rlandley@parallels.com>
> 
> The auth_unix cache needs to check network namespace when comparing
> addresses. Add field to struct ip_map and extra argument to
> __ip_map_lookup() so it has the information to do so, and add test.
> 
> Signed-off-by: Rob Landley <rlandley@parallels.com>
> ---
> 
>  net/sunrpc/svcauth_unix.c |   21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
> index 30916b0..63a2fa7 100644
> --- a/net/sunrpc/svcauth_unix.c
> +++ b/net/sunrpc/svcauth_unix.c
> @@ -14,6 +14,7 @@
>  #include <net/sock.h>
>  #include <net/ipv6.h>
>  #include <linux/kernel.h>
> +#include <linux/user_namespace.h>
>  #define RPCDBG_FACILITY	RPCDBG_AUTH
>  
>  #include <linux/sunrpc/clnt.h>
> @@ -94,6 +95,7 @@ struct ip_map {
>  	struct cache_head	h;
>  	char			m_class[8]; /* e.g. "nfsd" */
>  	struct in6_addr		m_addr;
> +	struct net		*m_net;
>  	struct unix_domain	*m_client;
>  #ifdef CONFIG_NFSD_DEPRECATED
>  	int			m_add_change;
> @@ -134,6 +136,7 @@ static int ip_map_match(struct cache_head *corig, struct cache_head *cnew)
>  	struct ip_map *orig = container_of(corig, struct ip_map, h);
>  	struct ip_map *new = container_of(cnew, struct ip_map, h);
>  	return strcmp(orig->m_class, new->m_class) == 0 &&
> +	       net_eq(orig->m_net, new->m_net) &&
>  	       ipv6_addr_equal(&orig->m_addr, &new->m_addr);
>  }
>  static void ip_map_init(struct cache_head *cnew, struct cache_head *citem)
> @@ -142,6 +145,7 @@ static void ip_map_init(struct cache_head *cnew, struct cache_head *citem)
>  	struct ip_map *item = container_of(citem, struct ip_map, h);
>  
>  	strcpy(new->m_class, item->m_class);
> +	new->m_net = item->m_net;

Does this need to take a reference?  Or is there no way for an
entry to outlive its netns?  It sort of looks like
svcauth_unix_info_release will ensure that doesn't happen, but
I'm not convinced because other parts of the kernel can get
to ip_map_init through the struct cache_detail.

>  	ipv6_addr_copy(&new->m_addr, &item->m_addr);
>  }
>  static void update(struct cache_head *cnew, struct cache_head *citem)
> @@ -186,7 +190,7 @@ static int ip_map_upcall(struct cache_detail *cd, struct cache_head *h)
>  	return sunrpc_cache_pipe_upcall(cd, h, ip_map_request);
>  }
>  
> -static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class, struct in6_addr *addr);
> +static struct ip_map *__ip_map_lookup(struct cache_detail *cd, struct net *net, char *class, struct in6_addr *addr);
>  static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm, struct unix_domain *udom, time_t expiry);
>  
>  static int ip_map_parse(struct cache_detail *cd,
> @@ -256,7 +260,8 @@ static int ip_map_parse(struct cache_detail *cd,
>  		dom = NULL;
>  
>  	/* IPv6 scope IDs are ignored for now */
> -	ipmp = __ip_map_lookup(cd, class, &sin6.sin6_addr);
> +	ipmp = __ip_map_lookup(cd, current->nsproxy->net_ns, class,
> +			       &sin6.sin6_addr);
>  	if (ipmp) {
>  		err = __ip_map_update(cd, ipmp,
>  			     container_of(dom, struct unix_domain, h),
> @@ -301,13 +306,14 @@ static int ip_map_show(struct seq_file *m,
>  }
>  
>  
> -static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class,
> -		struct in6_addr *addr)
> +static struct ip_map *__ip_map_lookup(struct cache_detail *cd, struct net *net,
> +		char *class, struct in6_addr *addr)
>  {
>  	struct ip_map ip;
>  	struct cache_head *ch;
>  
>  	strcpy(ip.m_class, class);
> +	ip.m_net = net;
>  	ipv6_addr_copy(&ip.m_addr, addr);
>  	ch = sunrpc_cache_lookup(cd, &ip.h,
>  				 hash_str(class, IP_HASHBITS) ^
> @@ -325,7 +331,7 @@ static inline struct ip_map *ip_map_lookup(struct net *net, char *class,
>  	struct sunrpc_net *sn;
>  
>  	sn = net_generic(net, sunrpc_net_id);
> -	return __ip_map_lookup(sn->ip_map_cache, class, addr);
> +	return __ip_map_lookup(sn->ip_map_cache, net, class, addr);
>  }
>  
>  static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm,
> @@ -748,8 +754,9 @@ svcauth_unix_set_client(struct svc_rqst *rqstp)
>  
>  	ipm = ip_map_cached_get(xprt);
>  	if (ipm == NULL)
> -		ipm = __ip_map_lookup(sn->ip_map_cache, rqstp->rq_server->sv_program->pg_class,
> -				    &sin6->sin6_addr);
> +		ipm = __ip_map_lookup(sn->ip_map_cache, net,
> +				      rqstp->rq_server->sv_program->pg_class,
> +				      &sin6->sin6_addr);
>  
>  	if (ipm == NULL)
>  		return SVC_DENIED;
> --
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Rob Landley April 8, 2011, 3:08 p.m. UTC | #2
On 04/04/2011 10:46 PM, Serge E. Hallyn wrote:
> Quoting Rob Landley (rlandley@parallels.com):
>> From: Rob Landley <rlandley@parallels.com>
>>
>> The auth_unix cache needs to check network namespace when comparing
>> addresses. Add field to struct ip_map and extra argument to
>> __ip_map_lookup() so it has the information to do so, and add test.
>>
>> Signed-off-by: Rob Landley <rlandley@parallels.com>
>> ---
>>
>>  net/sunrpc/svcauth_unix.c |   21 ++++++++++++++-------
>>  1 file changed, 14 insertions(+), 7 deletions(-)
>>
>> diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
>> index 30916b0..63a2fa7 100644
>> --- a/net/sunrpc/svcauth_unix.c
>> +++ b/net/sunrpc/svcauth_unix.c

code code code

>> @@ -142,6 +145,7 @@ static void ip_map_init(struct cache_head *cnew, struct cache_head *citem)
>>  	struct ip_map *item = container_of(citem, struct ip_map, h);
>>  
>>  	strcpy(new->m_class, item->m_class);
>> +	new->m_net = item->m_net;
> 
> Does this need to take a reference?  Or is there no way for an
> entry to outlive its netns?  It sort of looks like
> svcauth_unix_info_release will ensure that doesn't happen, but
> I'm not convinced because other parts of the kernel can get
> to ip_map_init through the struct cache_detail.

When I wrote this I thought the transport's get_net() and put_net()
would pin it, but after re-reading, the sunrpc code is disgustingly
convoluted enough that I can't easily reconstruct my earlier reasoning.
 I'll add a get_net() and put_net() just to not have to worry about it.

Thanks,

Rob
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Rob Landley April 11, 2011, 1:29 p.m. UTC | #3
On 04/08/2011 10:08 AM, Rob Landley wrote:
> On 04/04/2011 10:46 PM, Serge E. Hallyn wrote:
>> Does this need to take a reference?  Or is there no way for an
>> entry to outlive its netns?  It sort of looks like
>> svcauth_unix_info_release will ensure that doesn't happen, but
>> I'm not convinced because other parts of the kernel can get
>> to ip_map_init through the struct cache_detail.
> 
> When I wrote this I thought the transport's get_net() and put_net()
> would pin it, but after re-reading, the sunrpc code is disgustingly
> convoluted enough that I can't easily reconstruct my earlier reasoning.
>  I'll add a get_net() and put_net() just to not have to worry about it.

Ah-ha!

Stanislav Kinsbursky helped me reconstruct some of the reasoning: we
don't need to take a reference because we never actually dereference the
struct net *, all we do is feed them to net_eq() which just compares the
pointers for equality.  (The inline function exists so it can compile to
a constant "return 1" when configured out.)

So if the network context did go away (which still shouldn't happen
between the rpc_xprt and the struct nfs_client having references to it)
we still wouldn't have a use-after-free problem because we're not
looking at the memory, just the pointer.

So I shouldn't need to add get_net() and put_net() to the cache.  Sound
about right?

Rob
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Serge E. Hallyn April 11, 2011, 1:36 p.m. UTC | #4
Quoting Rob Landley (rlandley@parallels.com):
> On 04/08/2011 10:08 AM, Rob Landley wrote:
> > On 04/04/2011 10:46 PM, Serge E. Hallyn wrote:
> >> Does this need to take a reference?  Or is there no way for an
> >> entry to outlive its netns?  It sort of looks like
> >> svcauth_unix_info_release will ensure that doesn't happen, but
> >> I'm not convinced because other parts of the kernel can get
> >> to ip_map_init through the struct cache_detail.
> > 
> > When I wrote this I thought the transport's get_net() and put_net()
> > would pin it, but after re-reading, the sunrpc code is disgustingly
> > convoluted enough that I can't easily reconstruct my earlier reasoning.
> >  I'll add a get_net() and put_net() just to not have to worry about it.
> 
> Ah-ha!
> 
> Stanislav Kinsbursky helped me reconstruct some of the reasoning: we
> don't need to take a reference because we never actually dereference the
> struct net *, all we do is feed them to net_eq() which just compares the
> pointers for equality.  (The inline function exists so it can compile to
> a constant "return 1" when configured out.)
> 
> So if the network context did go away (which still shouldn't happen
> between the rpc_xprt and the struct nfs_client having references to it)
> we still wouldn't have a use-after-free problem because we're not
> looking at the memory, just the pointer.

Besides use-after-free, the other concern is an invalid net_eq()
result due to the * being re-used for a new netns.  I assume that's
deemed "super-duper impossible" again bc of the rpc_xprt/nfs_client
references to it?

> So I shouldn't need to add get_net() and put_net() to the cache.  Sound
> about right?

thanks,
-serge
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Alexey Dobriyan April 11, 2011, 1:57 p.m. UTC | #5
On Mon, Apr 11, 2011 at 4:36 PM, Serge E. Hallyn <serge@hallyn.com> wrote:

> Besides use-after-free, the other concern is an invalid net_eq()
> result due to the * being re-used for a new netns.

Exactly.

"struct net" dies last, no exceptions, anything different is a disaster.
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Rob Landley April 11, 2011, 5:45 p.m. UTC | #6
On 04/11/2011 08:57 AM, Alexey Dobriyan wrote:
> On Mon, Apr 11, 2011 at 4:36 PM, Serge E. Hallyn <serge@hallyn.com> wrote:
> 
>> Besides use-after-free, the other concern is an invalid net_eq()
>> result due to the * being re-used for a new netns.
> 
> Exactly.
> 
> "struct net" dies last, no exceptions, anything different is a disaster.

Actually the patch turns out to be irrelevant because Pavel made the
whole thing into a pernet subsystem, so it was already fixed in a
different way.  (Commit 2f72c9b7.  My bad, I initially started working
against an NFS tree with an older kernel version, this fix was to a
different source file so my patch still applied, and I just regression
tested that it worked, not that it still failed without it.  Just caught
it now.)

I actually did talk about addressing potential reuse of the net * in my
email with Stanislav (point of the patch was to allow one cache to
maintain two different contexts at the same time; a situation that
changed the meaning of an existing cache entry by requiring the old
context to go away didn't introduce any new problems that a single
context didn't already have due to DNAT, servers moving, administrators
changing credentials on the server).  But sort of a moot point now.

I believe the third patch can be dropped entirely.

Rob
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Patch
diff mbox

diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 30916b0..63a2fa7 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -14,6 +14,7 @@ 
 #include <net/sock.h>
 #include <net/ipv6.h>
 #include <linux/kernel.h>
+#include <linux/user_namespace.h>
 #define RPCDBG_FACILITY	RPCDBG_AUTH
 
 #include <linux/sunrpc/clnt.h>
@@ -94,6 +95,7 @@  struct ip_map {
 	struct cache_head	h;
 	char			m_class[8]; /* e.g. "nfsd" */
 	struct in6_addr		m_addr;
+	struct net		*m_net;
 	struct unix_domain	*m_client;
 #ifdef CONFIG_NFSD_DEPRECATED
 	int			m_add_change;
@@ -134,6 +136,7 @@  static int ip_map_match(struct cache_head *corig, struct cache_head *cnew)
 	struct ip_map *orig = container_of(corig, struct ip_map, h);
 	struct ip_map *new = container_of(cnew, struct ip_map, h);
 	return strcmp(orig->m_class, new->m_class) == 0 &&
+	       net_eq(orig->m_net, new->m_net) &&
 	       ipv6_addr_equal(&orig->m_addr, &new->m_addr);
 }
 static void ip_map_init(struct cache_head *cnew, struct cache_head *citem)
@@ -142,6 +145,7 @@  static void ip_map_init(struct cache_head *cnew, struct cache_head *citem)
 	struct ip_map *item = container_of(citem, struct ip_map, h);
 
 	strcpy(new->m_class, item->m_class);
+	new->m_net = item->m_net;
 	ipv6_addr_copy(&new->m_addr, &item->m_addr);
 }
 static void update(struct cache_head *cnew, struct cache_head *citem)
@@ -186,7 +190,7 @@  static int ip_map_upcall(struct cache_detail *cd, struct cache_head *h)
 	return sunrpc_cache_pipe_upcall(cd, h, ip_map_request);
 }
 
-static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class, struct in6_addr *addr);
+static struct ip_map *__ip_map_lookup(struct cache_detail *cd, struct net *net, char *class, struct in6_addr *addr);
 static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm, struct unix_domain *udom, time_t expiry);
 
 static int ip_map_parse(struct cache_detail *cd,
@@ -256,7 +260,8 @@  static int ip_map_parse(struct cache_detail *cd,
 		dom = NULL;
 
 	/* IPv6 scope IDs are ignored for now */
-	ipmp = __ip_map_lookup(cd, class, &sin6.sin6_addr);
+	ipmp = __ip_map_lookup(cd, current->nsproxy->net_ns, class,
+			       &sin6.sin6_addr);
 	if (ipmp) {
 		err = __ip_map_update(cd, ipmp,
 			     container_of(dom, struct unix_domain, h),
@@ -301,13 +306,14 @@  static int ip_map_show(struct seq_file *m,
 }
 
 
-static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class,
-		struct in6_addr *addr)
+static struct ip_map *__ip_map_lookup(struct cache_detail *cd, struct net *net,
+		char *class, struct in6_addr *addr)
 {
 	struct ip_map ip;
 	struct cache_head *ch;
 
 	strcpy(ip.m_class, class);
+	ip.m_net = net;
 	ipv6_addr_copy(&ip.m_addr, addr);
 	ch = sunrpc_cache_lookup(cd, &ip.h,
 				 hash_str(class, IP_HASHBITS) ^
@@ -325,7 +331,7 @@  static inline struct ip_map *ip_map_lookup(struct net *net, char *class,
 	struct sunrpc_net *sn;
 
 	sn = net_generic(net, sunrpc_net_id);
-	return __ip_map_lookup(sn->ip_map_cache, class, addr);
+	return __ip_map_lookup(sn->ip_map_cache, net, class, addr);
 }
 
 static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm,
@@ -748,8 +754,9 @@  svcauth_unix_set_client(struct svc_rqst *rqstp)
 
 	ipm = ip_map_cached_get(xprt);
 	if (ipm == NULL)
-		ipm = __ip_map_lookup(sn->ip_map_cache, rqstp->rq_server->sv_program->pg_class,
-				    &sin6->sin6_addr);
+		ipm = __ip_map_lookup(sn->ip_map_cache, net,
+				      rqstp->rq_server->sv_program->pg_class,
+				      &sin6->sin6_addr);
 
 	if (ipm == NULL)
 		return SVC_DENIED;