[PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Peter Oskolkov]

Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
removes port-only listener lookups. This caused segfaults in DCCP
lookups because DCCP did not initialize the (addr,port) hashtable.

This patch adds said initialization.

The only non-trivial issue here is the size of the new hashtable.
It seemed reasonable to make it match the size of the port-only
hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
parameters to inet_hashinfo2_init() match those used in TCP.

V2 changes: marked inet_hashinfo2_init as an exported symbol
so that DCCP compiles when configured as a module.

Tested: syzcaller issues fixed; the second patch in the patchset
        tests that DCCP lookups work correctly.

Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
Reported-by: syzcaller <syzkaller@googlegroups.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
---
 net/dccp/proto.c           | 3 +++
 net/ipv4/inet_hashtables.c | 1 +
 2 files changed, 4 insertions(+)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 658cd32bb7b37..be0b223aa8625 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1141,6 +1141,9 @@ static int __init dccp_init(void)
 		goto out_fail;
 	rc = -ENOBUFS;
 	inet_hashinfo_init(&dccp_hashinfo);
+	inet_hashinfo2_init(&dccp_hashinfo, "dccp_listen_portaddr_hash",
+			    INET_LHTABLE_SIZE, 21,  /* one slot per 2 MB*/
+			    0, 64 * 1024);
 	dccp_hashinfo.bind_bucket_cachep =
 		kmem_cache_create("dccp_bind_bucket",
 				  sizeof(struct inet_bind_bucket), 0,
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index cd03ab42705b4..2445614de6a76 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -785,6 +785,7 @@ void __init inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
 		h->lhash2[i].count = 0;
 	}
 }
+EXPORT_SYMBOL_GPL(inet_hashinfo2_init);
 
 int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
 {
-- 
2.20.0.405.gbc1bbc6f85-goog

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Eric Dumazet]

On 12/16/2018 03:42 PM, Peter Oskolkov wrote:
> Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> removes port-only listener lookups. This caused segfaults in DCCP
> lookups because DCCP did not initialize the (addr,port) hashtable.
> 
> This patch adds said initialization.
> 
> The only non-trivial issue here is the size of the new hashtable.
> It seemed reasonable to make it match the size of the port-only
> hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
> parameters to inet_hashinfo2_init() match those used in TCP.
> 
> V2 changes: marked inet_hashinfo2_init as an exported symbol
> so that DCCP compiles when configured as a module.
> 
> Tested: syzcaller issues fixed; the second patch in the patchset
>         tests that DCCP lookups work correctly.
> 
> Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"


Strange, I would say bug was brought by commit 61b7c691c731
("inet: Add a 2nd listener hashtable (port+addr)")

The secondary hash table would have been used anyway if some application (syzkaller-like)
had been using DCCP a bit more, to the point the second hash table would have been used.

With more than 10 listeners on one bucket, code in inet6_lookup_listener() would
have attempted to deref a NULL pointer.

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Peter Oskolkov]

I guess DCCP is not used to the extent that 10 listeners per bucket
happen in real life scenarios, so the issue is purely theoretical; as
my patch would cause a sefgault for even a single listening dccp
socket, I felt it was my patch that the "Fixes" tag should refer to.

On Sun, Dec 16, 2018 at 9:51 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 12/16/2018 03:42 PM, Peter Oskolkov wrote:
> > Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> > removes port-only listener lookups. This caused segfaults in DCCP
> > lookups because DCCP did not initialize the (addr,port) hashtable.
> >
> > This patch adds said initialization.
> >
> > The only non-trivial issue here is the size of the new hashtable.
> > It seemed reasonable to make it match the size of the port-only
> > hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
> > parameters to inet_hashinfo2_init() match those used in TCP.
> >
> > V2 changes: marked inet_hashinfo2_init as an exported symbol
> > so that DCCP compiles when configured as a module.
> >
> > Tested: syzcaller issues fixed; the second patch in the patchset
> >         tests that DCCP lookups work correctly.
> >
> > Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
>
>
> Strange, I would say bug was brought by commit 61b7c691c731
> ("inet: Add a 2nd listener hashtable (port+addr)")
>
> The secondary hash table would have been used anyway if some application (syzkaller-like)
> had been using DCCP a bit more, to the point the second hash table would have been used.
>
> With more than 10 listeners on one bucket, code in inet6_lookup_listener() would
> have attempted to deref a NULL pointer.

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Eric Dumazet]

On Sun, Dec 16, 2018 at 10:35 PM Peter Oskolkov <posk.devel@gmail.com> wrote:
>
> I guess DCCP is not used to the extent that 10 listeners per bucket
> happen in real life scenarios, so the issue is purely theoretical; as
> my patch would cause a sefgault for even a single listening dccp
> socket, I felt it was my patch that the "Fixes" tag should refer to.
>

Problem is : any host with a buggy kernel can trivially crash if a
malicious application
knows about this bug and exploit it.

This means we need to backport this fix to all kernels up to the real
root cause,
not only net-next on which your patch revealed this old bug.

Therefore we need a correct Fixes: tag so that proper stable
submissions can be done.

The Fixes: tag accuracy is paramount.

Thanks.

> On Sun, Dec 16, 2018 at 9:51 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >
> >
> >
> > On 12/16/2018 03:42 PM, Peter Oskolkov wrote:
> > > Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> > > removes port-only listener lookups. This caused segfaults in DCCP
> > > lookups because DCCP did not initialize the (addr,port) hashtable.
> > >
> > > This patch adds said initialization.
> > >
> > > The only non-trivial issue here is the size of the new hashtable.
> > > It seemed reasonable to make it match the size of the port-only
> > > hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
> > > parameters to inet_hashinfo2_init() match those used in TCP.
> > >
> > > V2 changes: marked inet_hashinfo2_init as an exported symbol
> > > so that DCCP compiles when configured as a module.
> > >
> > > Tested: syzcaller issues fixed; the second patch in the patchset
> > >         tests that DCCP lookups work correctly.
> > >
> > > Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> >
> >
> > Strange, I would say bug was brought by commit 61b7c691c731
> > ("inet: Add a 2nd listener hashtable (port+addr)")
> >
> > The secondary hash table would have been used anyway if some application (syzkaller-like)
> > had been using DCCP a bit more, to the point the second hash table would have been used.
> >
> > With more than 10 listeners on one bucket, code in inet6_lookup_listener() would
> > have attempted to deref a NULL pointer.

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Peter Oskolkov]

On Sun, Dec 16, 2018 at 10:41 PM Eric Dumazet <edumazet@google.com> wrote:
>
> On Sun, Dec 16, 2018 at 10:35 PM Peter Oskolkov <posk.devel@gmail.com> wrote:
> >
> > I guess DCCP is not used to the extent that 10 listeners per bucket
> > happen in real life scenarios, so the issue is purely theoretical; as
> > my patch would cause a sefgault for even a single listening dccp
> > socket, I felt it was my patch that the "Fixes" tag should refer to.
> >
>
> Problem is : any host with a buggy kernel can trivially crash if a
> malicious application
> knows about this bug and exploit it.
>
> This means we need to backport this fix to all kernels up to the real
> root cause,
> not only net-next on which your patch revealed this old bug.
>
> Therefore we need a correct Fixes: tag so that proper stable
> submissions can be done.
>
> The Fixes: tag accuracy is paramount.

Make sense. I'll re-send the patch withe the correct Fixes tag asap.

>
> Thanks.
>
> > On Sun, Dec 16, 2018 at 9:51 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > >
> > >
> > >
> > > On 12/16/2018 03:42 PM, Peter Oskolkov wrote:
> > > > Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> > > > removes port-only listener lookups. This caused segfaults in DCCP
> > > > lookups because DCCP did not initialize the (addr,port) hashtable.
> > > >
> > > > This patch adds said initialization.
> > > >
> > > > The only non-trivial issue here is the size of the new hashtable.
> > > > It seemed reasonable to make it match the size of the port-only
> > > > hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
> > > > parameters to inet_hashinfo2_init() match those used in TCP.
> > > >
> > > > V2 changes: marked inet_hashinfo2_init as an exported symbol
> > > > so that DCCP compiles when configured as a module.
> > > >
> > > > Tested: syzcaller issues fixed; the second patch in the patchset
> > > >         tests that DCCP lookups work correctly.
> > > >
> > > > Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> > >
> > >
> > > Strange, I would say bug was brought by commit 61b7c691c731
> > > ("inet: Add a 2nd listener hashtable (port+addr)")
> > >
> > > The secondary hash table would have been used anyway if some application (syzkaller-like)
> > > had been using DCCP a bit more, to the point the second hash table would have been used.
> > >
> > > With more than 10 listeners on one bucket, code in inet6_lookup_listener() would
> > > have attempted to deref a NULL pointer.

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Peter Oskolkov]

On Sun, Dec 16, 2018 at 10:46 PM Peter Oskolkov <posk.devel@gmail.com> wrote:
>
> On Sun, Dec 16, 2018 at 10:41 PM Eric Dumazet <edumazet@google.com> wrote:
> >
> > On Sun, Dec 16, 2018 at 10:35 PM Peter Oskolkov <posk.devel@gmail.com> wrote:
> > >
> > > I guess DCCP is not used to the extent that 10 listeners per bucket
> > > happen in real life scenarios, so the issue is purely theoretical; as
> > > my patch would cause a sefgault for even a single listening dccp
> > > socket, I felt it was my patch that the "Fixes" tag should refer to.
> > >
> >
> > Problem is : any host with a buggy kernel can trivially crash if a
> > malicious application
> > knows about this bug and exploit it.
> >
> > This means we need to backport this fix to all kernels up to the real
> > root cause,
> > not only net-next on which your patch revealed this old bug.
> >
> > Therefore we need a correct Fixes: tag so that proper stable
> > submissions can be done.
> >
> > The Fixes: tag accuracy is paramount.
>
> Make sense. I'll re-send the patch withe the correct Fixes tag asap.

Actually, no: the earlier patch has this condition:

+       if (ilb->count <= 10 || !hashinfo->lhash2)
+               goto port_lookup;

that checks if lhash2 is initialized. So the bug is in my patch.

>
> >
> > Thanks.
> >
> > > On Sun, Dec 16, 2018 at 9:51 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > > >
> > > >
> > > >
> > > > On 12/16/2018 03:42 PM, Peter Oskolkov wrote:
> > > > > Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> > > > > removes port-only listener lookups. This caused segfaults in DCCP
> > > > > lookups because DCCP did not initialize the (addr,port) hashtable.
> > > > >
> > > > > This patch adds said initialization.
> > > > >
> > > > > The only non-trivial issue here is the size of the new hashtable.
> > > > > It seemed reasonable to make it match the size of the port-only
> > > > > hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
> > > > > parameters to inet_hashinfo2_init() match those used in TCP.
> > > > >
> > > > > V2 changes: marked inet_hashinfo2_init as an exported symbol
> > > > > so that DCCP compiles when configured as a module.
> > > > >
> > > > > Tested: syzcaller issues fixed; the second patch in the patchset
> > > > >         tests that DCCP lookups work correctly.
> > > > >
> > > > > Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> > > >
> > > >
> > > > Strange, I would say bug was brought by commit 61b7c691c731
> > > > ("inet: Add a 2nd listener hashtable (port+addr)")
> > > >
> > > > The secondary hash table would have been used anyway if some application (syzkaller-like)
> > > > had been using DCCP a bit more, to the point the second hash table would have been used.
> > > >
> > > > With more than 10 listeners on one bucket, code in inet6_lookup_listener() would
> > > > have attempted to deref a NULL pointer.

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[Eric Dumazet]

On 12/16/2018 10:49 PM, Peter Oskolkov wrote:
 
> Actually, no: the earlier patch has this condition:
> 
> +       if (ilb->count <= 10 || !hashinfo->lhash2)
> +               goto port_lookup;
> 
> that checks if lhash2 is initialized. So the bug is in my patch.

Great, thanks for double checking.

Re: [PATCH net-next v2] net: dccp: initialize (addr,port) listening hashtable

[David Miller]

From: Peter Oskolkov <posk@google.com>
Date: Sun, 16 Dec 2018 15:42:48 -0800

> Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> removes port-only listener lookups. This caused segfaults in DCCP
> lookups because DCCP did not initialize the (addr,port) hashtable.
> 
> This patch adds said initialization.
> 
> The only non-trivial issue here is the size of the new hashtable.
> It seemed reasonable to make it match the size of the port-only
> hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
> parameters to inet_hashinfo2_init() match those used in TCP.
> 
> V2 changes: marked inet_hashinfo2_init as an exported symbol
> so that DCCP compiles when configured as a module.
> 
> Tested: syzcaller issues fixed; the second patch in the patchset
>         tests that DCCP lookups work correctly.
> 
> Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
> Reported-by: syzcaller <syzkaller@googlegroups.com>
> Signed-off-by: Peter Oskolkov <posk@google.com>

Applied, thanks.