[PATCH 0/3] SUNRPC/svc: fix gss flavour registration problems.

[PATCH 0/3] SUNRPC/svc: fix gss flavour registration problems.

[NeilBrown]

As reported in
 https://bugzilla.kernel.org/show_bug.cgi?id=206651
there are problems with sunrpc/svc flavour registration.

This can be demonstrated as a memory-leak if you load the
rpcsec_gss_krb5 module, then unload the sunrpc module and all
dependents.  This action leaks 3 kmalloc-64 slab entires, and some
strings.

The possible consequences are worse.  If only unload rpcsec_gss_krb5
and reload just that, it will allow the old registered flavour handlers
to be used, and they will include pointers into memory which has since
been freed and possibly reused.  This can result in undesired
behaviour.

The first patch makes the leak apparent with a WARNing, the second
prevents it but also prevents module reload, the third removes the
incorrect behaviour so the module can be safely unloaded and reloaded.

I think all are suitable for -stable, but I haven't determined
appropriate 'Fixes:' tags.

NeilBrown

---

NeilBrown (3):
      sunrpc: check that domain table is empty at module unload.
      sunrpc: svcauth_gss_register_pseudoflavor must reject duplicate registrations.
      sunrpc: clean up properly in gss_mech_unregister()


 include/linux/sunrpc/gss_api.h        |    1 +
 include/linux/sunrpc/svcauth_gss.h    |    3 ++-
 net/sunrpc/auth_gss/gss_mech_switch.c |   12 +++++++++---
 net/sunrpc/auth_gss/svcauth_gss.c     |   17 ++++++++++-------
 net/sunrpc/sunrpc.h                   |    1 +
 net/sunrpc/sunrpc_syms.c              |    2 ++
 net/sunrpc/svcauth.c                  |   18 ++++++++++++++++++
 7 files changed, 43 insertions(+), 11 deletions(-)

--
Signature

[PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[NeilBrown]

The domain table should be empty at module unload.  If it isn't there is
a bug somewhere.  So check and report.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
---
 net/sunrpc/sunrpc.h      |    1 +
 net/sunrpc/sunrpc_syms.c |    2 ++
 net/sunrpc/svcauth.c     |   18 ++++++++++++++++++
 3 files changed, 21 insertions(+)

diff --git a/net/sunrpc/sunrpc.h b/net/sunrpc/sunrpc.h
index 47a756503d11..f6fe2e6cd65a 100644
--- a/net/sunrpc/sunrpc.h
+++ b/net/sunrpc/sunrpc.h
@@ -52,4 +52,5 @@ static inline int sock_is_loopback(struct sock *sk)
 
 int rpc_clients_notifier_register(void);
 void rpc_clients_notifier_unregister(void);
+void auth_domain_cleanup(void);
 #endif /* _NET_SUNRPC_SUNRPC_H */
diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
index f9edaa9174a4..236fadc4a439 100644
--- a/net/sunrpc/sunrpc_syms.c
+++ b/net/sunrpc/sunrpc_syms.c
@@ -23,6 +23,7 @@
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/sunrpc/xprtsock.h>
 
+#include "sunrpc.h"
 #include "netns.h"
 
 unsigned int sunrpc_net_id;
@@ -131,6 +132,7 @@ cleanup_sunrpc(void)
 	unregister_rpc_pipefs();
 	rpc_destroy_mempool();
 	unregister_pernet_subsys(&sunrpc_net_ops);
+	auth_domain_cleanup();
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 	rpc_unregister_sysctl();
 #endif
diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
index 552617e3467b..477890e8b9d8 100644
--- a/net/sunrpc/svcauth.c
+++ b/net/sunrpc/svcauth.c
@@ -205,3 +205,21 @@ struct auth_domain *auth_domain_find(char *name)
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(auth_domain_find);
+
+void auth_domain_cleanup(void)
+{
+	/* There should be no auth_domains left at module unload */
+	int h;
+	bool found = false;
+
+	for (h = 0; h < DN_HASHMAX; h++) {
+		struct auth_domain *hp;
+
+		hlist_for_each_entry(hp, auth_domain_table+h, hash) {
+			found = true;
+			printk(KERN_WARNING "sunrpc: domain %s still present at module unload.\n",
+			       hp->name);
+		}
+	}
+	WARN(found, "sunrpc: auth_domain_table not clean -> memory leak\n");
+}

[PATCH 2/3] sunrpc: svcauth_gss_register_pseudoflavor must reject duplicate registrations.

[NeilBrown]

There is no valid case for supporting duplicate pseudoflavor
registrations.
Currently the silent acceptance of such registrations is hiding a bug.
The rpcsec_gss_krb5 module registers 2 flavours but does not unregister
them, so if you load, unload, reload the module, it will happily
continue to use the old registration which now has pointers to the
memory were the module was originally loaded.  This could lead to
unexpected results.

So disallow duplicate registrations.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
---
 net/sunrpc/auth_gss/svcauth_gss.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 50d93c49ef1a..4aaaad794edb 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -826,9 +826,12 @@ svcauth_gss_register_pseudoflavor(u32 pseudoflavor, char * name)
 	new->h.flavour = &svcauthops_gss;
 	new->pseudoflavor = pseudoflavor;
 
-	stat = 0;
 	test = auth_domain_lookup(name, &new->h);
 	if (test != &new->h) { /* Duplicate registration */
+		printk(KERN_WARNING
+		       "SUNRPC:svcauth_gss: duplicate pseudo flavour registration of %s\n",
+		       name);
+		stat = -EALREADY;
 		auth_domain_put(test);
 		kfree(new->h.name);
 		goto out_free_dom;

[PATCH 3/3] sunrpc: clean up properly in gss_mech_unregister()

[NeilBrown]

gss_mech_register() calls svcauth_gss_register_pseudoflavor() for each
flavour, but gss_mech_unregister() does not call auth_domain_put().
This is unbalanced and makes it impossible to reload the module.

Change svcauth_gss_register_pseudoflavor() to return the registered
auth_domain, and save it for later release.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
---
 include/linux/sunrpc/gss_api.h        |    1 +
 include/linux/sunrpc/svcauth_gss.h    |    3 ++-
 net/sunrpc/auth_gss/gss_mech_switch.c |   12 +++++++++---
 net/sunrpc/auth_gss/svcauth_gss.c     |   12 ++++++------
 4 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/include/linux/sunrpc/gss_api.h b/include/linux/sunrpc/gss_api.h
index bc07e51f20d1..bf4ac8a0268c 100644
--- a/include/linux/sunrpc/gss_api.h
+++ b/include/linux/sunrpc/gss_api.h
@@ -84,6 +84,7 @@ struct pf_desc {
 	u32	service;
 	char	*name;
 	char	*auth_domain_name;
+	struct auth_domain *domain;
 	bool	datatouch;
 };
 
diff --git a/include/linux/sunrpc/svcauth_gss.h b/include/linux/sunrpc/svcauth_gss.h
index ca39a388dc22..8983628b10ff 100644
--- a/include/linux/sunrpc/svcauth_gss.h
+++ b/include/linux/sunrpc/svcauth_gss.h
@@ -20,7 +20,8 @@ int gss_svc_init(void);
 void gss_svc_shutdown(void);
 int gss_svc_init_net(struct net *net);
 void gss_svc_shutdown_net(struct net *net);
-int svcauth_gss_register_pseudoflavor(u32 pseudoflavor, char * name);
+struct auth_domain *svcauth_gss_register_pseudoflavor(u32 pseudoflavor,
+						      char * name);
 u32 svcauth_gss_flavor(struct auth_domain *dom);
 
 #endif /* _LINUX_SUNRPC_SVCAUTH_GSS_H */
diff --git a/net/sunrpc/auth_gss/gss_mech_switch.c b/net/sunrpc/auth_gss/gss_mech_switch.c
index 69316ab1b9fa..fae632da1058 100644
--- a/net/sunrpc/auth_gss/gss_mech_switch.c
+++ b/net/sunrpc/auth_gss/gss_mech_switch.c
@@ -37,6 +37,8 @@ gss_mech_free(struct gss_api_mech *gm)
 
 	for (i = 0; i < gm->gm_pf_num; i++) {
 		pf = &gm->gm_pfs[i];
+		if (pf->domain)
+			auth_domain_put(pf->domain);
 		kfree(pf->auth_domain_name);
 		pf->auth_domain_name = NULL;
 	}
@@ -59,6 +61,7 @@ make_auth_domain_name(char *name)
 static int
 gss_mech_svc_setup(struct gss_api_mech *gm)
 {
+	struct auth_domain *dom;
 	struct pf_desc *pf;
 	int i, status;
 
@@ -68,10 +71,13 @@ gss_mech_svc_setup(struct gss_api_mech *gm)
 		status = -ENOMEM;
 		if (pf->auth_domain_name == NULL)
 			goto out;
-		status = svcauth_gss_register_pseudoflavor(pf->pseudoflavor,
-							pf->auth_domain_name);
-		if (status)
+		dom = svcauth_gss_register_pseudoflavor(
+			pf->pseudoflavor, pf->auth_domain_name);
+		if (IS_ERR(dom)) {
+			status = PTR_ERR(dom);
 			goto out;
+		}
+		pf->domain = dom;
 	}
 	return 0;
 out:
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 4aaaad794edb..4441920c3d04 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -809,7 +809,7 @@ u32 svcauth_gss_flavor(struct auth_domain *dom)
 
 EXPORT_SYMBOL_GPL(svcauth_gss_flavor);
 
-int
+struct auth_domain *
 svcauth_gss_register_pseudoflavor(u32 pseudoflavor, char * name)
 {
 	struct gss_domain	*new;
@@ -833,17 +833,17 @@ svcauth_gss_register_pseudoflavor(u32 pseudoflavor, char * name)
 		       name);
 		stat = -EALREADY;
 		auth_domain_put(test);
-		kfree(new->h.name);
-		goto out_free_dom;
+		goto out_free_name;
 	}
-	return 0;
+	return test;
 
+out_free_name:
+	kfree(new->h.name);
 out_free_dom:
 	kfree(new);
 out:
-	return stat;
+	return ERR_PTR(stat);
 }
-
 EXPORT_SYMBOL_GPL(svcauth_gss_register_pseudoflavor);
 
 static inline int

Re: [PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3223 bytes --]

Hi NeilBrown,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on nfsd/nfsd-next]
[also build test WARNING on nfs/linux-next cel/for-next v5.7-rc6 next-20200519]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/NeilBrown/SUNRPC-svc-fix-gss-flavour-registration-problems/20200521-112443
base:   git://linux-nfs.org/~bfields/linux.git nfsd-next
config: um-allmodconfig (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce (this is a W=1 build):
        # save the attached .config to linux build tree
        make ARCH=um 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

cc1: warning: arch/um/include/uapi: No such file or directory [-Wmissing-include-dirs]
In file included from include/linux/uaccess.h:11:0,
from include/linux/sched/task.h:11,
from include/linux/sched/signal.h:9,
from include/linux/sunrpc/types.h:14,
from net/sunrpc/svcauth.c:15:
arch/um/include/asm/uaccess.h: In function '__access_ok':
arch/um/include/asm/uaccess.h:17:29: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
(((unsigned long) (addr) >= FIXADDR_USER_START) &&                                 ^
arch/um/include/asm/uaccess.h:45:3: note: in expansion of macro '__access_ok_vsyscall'
__access_ok_vsyscall(addr, size) ||
^~~~~~~~~~~~~~~~~~~~
In file included from include/linux/kernel.h:11:0,
from include/linux/list.h:9,
from include/linux/module.h:12,
from net/sunrpc/svcauth.c:14:
include/asm-generic/fixmap.h: In function 'fix_to_virt':
include/asm-generic/fixmap.h:32:19: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
^
include/linux/compiler.h:330:9: note: in definition of macro '__compiletime_assert'
if (!(condition))                 ^~~~~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
^~~~~~~~~~~~~~~~
include/asm-generic/fixmap.h:32:2: note: in expansion of macro 'BUILD_BUG_ON'
BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
^~~~~~~~~~~~
net/sunrpc/svcauth.c: At top level:
>> net/sunrpc/svcauth.c:209:6: warning: no previous prototype for 'auth_domain_cleanup' [-Wmissing-prototypes]
void auth_domain_cleanup(void)
^~~~~~~~~~~~~~~~~~~

vim +/auth_domain_cleanup +209 net/sunrpc/svcauth.c

   208	
 > 209	void auth_domain_cleanup(void)

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 22561 bytes --]

Re: [PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1900 bytes --]

Hi NeilBrown,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on nfsd/nfsd-next]
[also build test WARNING on nfs/linux-next v5.7-rc6 next-20200519]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/NeilBrown/SUNRPC-svc-fix-gss-flavour-registration-problems/20200521-112443
base:   git://linux-nfs.org/~bfields/linux.git nfsd-next
config: arm-randconfig-r035-20200521 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 3393cc4cebf9969db94dc424b7a2b6195589c33b)
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> net/sunrpc/svcauth.c:209:6: warning: no previous prototype for function 'auth_domain_cleanup' [-Wmissing-prototypes]
void auth_domain_cleanup(void)
^
net/sunrpc/svcauth.c:209:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void auth_domain_cleanup(void)
^
static
1 warning generated.

vim +/auth_domain_cleanup +209 net/sunrpc/svcauth.c

   208	
 > 209	void auth_domain_cleanup(void)

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 39799 bytes --]

Re: [PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[Chuck Lever]

Hi Neil!

Thanks for the patches. Seems to me like a good fix overall.

Judging by the syzbot e-mail, you might be posting a refresh of this
patch series, so I proffer a few minor review comments below.


> On May 20, 2020, at 11:21 PM, NeilBrown <neilb@suse.de> wrote:
> 
> The domain table should be empty at module unload.  If it isn't there is
> a bug somewhere.  So check and report.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
> Cc: stable@vger.kernel.org
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
> net/sunrpc/sunrpc.h      |    1 +
> net/sunrpc/sunrpc_syms.c |    2 ++
> net/sunrpc/svcauth.c     |   18 ++++++++++++++++++
> 3 files changed, 21 insertions(+)
> 
> diff --git a/net/sunrpc/sunrpc.h b/net/sunrpc/sunrpc.h
> index 47a756503d11..f6fe2e6cd65a 100644
> --- a/net/sunrpc/sunrpc.h
> +++ b/net/sunrpc/sunrpc.h
> @@ -52,4 +52,5 @@ static inline int sock_is_loopback(struct sock *sk)
> 
> int rpc_clients_notifier_register(void);
> void rpc_clients_notifier_unregister(void);
> +void auth_domain_cleanup(void);
> #endif /* _NET_SUNRPC_SUNRPC_H */
> diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
> index f9edaa9174a4..236fadc4a439 100644
> --- a/net/sunrpc/sunrpc_syms.c
> +++ b/net/sunrpc/sunrpc_syms.c
> @@ -23,6 +23,7 @@
> #include <linux/sunrpc/rpc_pipe_fs.h>
> #include <linux/sunrpc/xprtsock.h>
> 
> +#include "sunrpc.h"
> #include "netns.h"
> 
> unsigned int sunrpc_net_id;
> @@ -131,6 +132,7 @@ cleanup_sunrpc(void)
> 	unregister_rpc_pipefs();
> 	rpc_destroy_mempool();
> 	unregister_pernet_subsys(&sunrpc_net_ops);
> +	auth_domain_cleanup();
> #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
> 	rpc_unregister_sysctl();
> #endif
> diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
> index 552617e3467b..477890e8b9d8 100644
> --- a/net/sunrpc/svcauth.c
> +++ b/net/sunrpc/svcauth.c
> @@ -205,3 +205,21 @@ struct auth_domain *auth_domain_find(char *name)
> 	return NULL;
> }
> EXPORT_SYMBOL_GPL(auth_domain_find);
> +
> +void auth_domain_cleanup(void)
> +{
> +	/* There should be no auth_domains left at module unload */

Since this is a globally-visible function, could you move this comment
into a Doxy documenting comment before the function? It should make clear
that the purpose of this function is only for debugging.


> +	int h;
> +	bool found = false;
> +
> +	for (h = 0; h < DN_HASHMAX; h++) {
> +		struct auth_domain *hp;
> +
> +		hlist_for_each_entry(hp, auth_domain_table+h, hash) {
> +			found = true;
> +			printk(KERN_WARNING "sunrpc: domain %s still present at module unload.\n",
> +			       hp->name);

Nit: Documentation/process/coding-style.rst recommends using the pr_warn()
macro here (and equivalents in other patches)... And note that "svc:" is
the conventional prefix for server-side warnings.

I'm wondering... is it safe to release an auth_domain here if one is found,
so that it is not actually orphaned? The warning is information for
developers; there's nothing, say, an administrator can do about this
situation.


> +		}
> +	}
> +	WARN(found, "sunrpc: auth_domain_table not clean -> memory leak\n");

Not sure a stack trace in addition to the above warning messages adds
relevant information. Can you provide a little justification for that?

Thanks!


> +}
> 
> 

--
Chuck Lever

Re: [PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 4109 bytes --]

On Thu, May 21 2020, Chuck Lever wrote:

> Hi Neil!
>
> Thanks for the patches. Seems to me like a good fix overall.
>
> Judging by the syzbot e-mail, you might be posting a refresh of this
> patch series, so I proffer a few minor review comments below.
>
>
>> On May 20, 2020, at 11:21 PM, NeilBrown <neilb@suse.de> wrote:
>> 
>> The domain table should be empty at module unload.  If it isn't there is
>> a bug somewhere.  So check and report.
>> 
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
>> Cc: stable@vger.kernel.org
>> Signed-off-by: NeilBrown <neilb@suse.de>
>> ---
>> net/sunrpc/sunrpc.h      |    1 +
>> net/sunrpc/sunrpc_syms.c |    2 ++
>> net/sunrpc/svcauth.c     |   18 ++++++++++++++++++
>> 3 files changed, 21 insertions(+)
>> 
>> diff --git a/net/sunrpc/sunrpc.h b/net/sunrpc/sunrpc.h
>> index 47a756503d11..f6fe2e6cd65a 100644
>> --- a/net/sunrpc/sunrpc.h
>> +++ b/net/sunrpc/sunrpc.h
>> @@ -52,4 +52,5 @@ static inline int sock_is_loopback(struct sock *sk)
>> 
>> int rpc_clients_notifier_register(void);
>> void rpc_clients_notifier_unregister(void);
>> +void auth_domain_cleanup(void);
>> #endif /* _NET_SUNRPC_SUNRPC_H */
>> diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
>> index f9edaa9174a4..236fadc4a439 100644
>> --- a/net/sunrpc/sunrpc_syms.c
>> +++ b/net/sunrpc/sunrpc_syms.c
>> @@ -23,6 +23,7 @@
>> #include <linux/sunrpc/rpc_pipe_fs.h>
>> #include <linux/sunrpc/xprtsock.h>
>> 
>> +#include "sunrpc.h"
>> #include "netns.h"
>> 
>> unsigned int sunrpc_net_id;
>> @@ -131,6 +132,7 @@ cleanup_sunrpc(void)
>> 	unregister_rpc_pipefs();
>> 	rpc_destroy_mempool();
>> 	unregister_pernet_subsys(&sunrpc_net_ops);
>> +	auth_domain_cleanup();
>> #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
>> 	rpc_unregister_sysctl();
>> #endif
>> diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
>> index 552617e3467b..477890e8b9d8 100644
>> --- a/net/sunrpc/svcauth.c
>> +++ b/net/sunrpc/svcauth.c
>> @@ -205,3 +205,21 @@ struct auth_domain *auth_domain_find(char *name)
>> 	return NULL;
>> }
>> EXPORT_SYMBOL_GPL(auth_domain_find);
>> +
>> +void auth_domain_cleanup(void)
>> +{
>> +	/* There should be no auth_domains left at module unload */
>
> Since this is a globally-visible function, could you move this comment
> into a Doxy documenting comment before the function? It should make clear
> that the purpose of this function is only for debugging.

I wouldn't call it "globally-visible" as it isn't exported, and isn't
even declared in linux/include/...
But a Doxy comment is probably justified.

>
>
>> +	int h;
>> +	bool found = false;
>> +
>> +	for (h = 0; h < DN_HASHMAX; h++) {
>> +		struct auth_domain *hp;
>> +
>> +		hlist_for_each_entry(hp, auth_domain_table+h, hash) {
>> +			found = true;
>> +			printk(KERN_WARNING "sunrpc: domain %s still present at module unload.\n",
>> +			       hp->name);
>
> Nit: Documentation/process/coding-style.rst recommends using the pr_warn()
> macro here (and equivalents in other patches)... And note that "svc:" is
> the conventional prefix for server-side warnings.

I'll fix that, thanks.

>
> I'm wondering... is it safe to release an auth_domain here if one is found,
> so that it is not actually orphaned? The warning is information for
> developers; there's nothing, say, an administrator can do about this
> situation.

I don't think it is safe to release the domain.  The ->release()
function could be in a module that has already been unloaded.

>
>
>> +		}
>> +	}
>> +	WARN(found, "sunrpc: auth_domain_table not clean -> memory leak\n");
>
> Not sure a stack trace in addition to the above warning messages adds
> relevant information. Can you provide a little justification for that?

I guess so.  I wanted a nice loud warning - and people tend to notice
stack traces more than they notice printks - it was an attempt at human
engineering :-)

Maybe I'll just leave it as pr_warn...

Thanks for the review.

NeilBrown


>
> Thanks!
>
>
>> +}
>> 
>> 
>
> --
> Chuck Lever

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]

Re: [PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[Chuck Lever]

> On May 21, 2020, at 7:45 PM, NeilBrown <neilb@suse.de> wrote:
> 
> On Thu, May 21 2020, Chuck Lever wrote:
> 
>> Hi Neil!
>> 
>> Thanks for the patches. Seems to me like a good fix overall.
>> 
>> Judging by the syzbot e-mail, you might be posting a refresh of this
>> patch series, so I proffer a few minor review comments below.
>> 
>> 
>>>> On May 20, 2020, at 11:21 PM, NeilBrown <neilb@suse.de> wrote:
>>> 
>>> The domain table should be empty at module unload.  If it isn't there is
>>> a bug somewhere.  So check and report.
>>> 
>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: NeilBrown <neilb@suse.de>
>>> ---
>>> net/sunrpc/sunrpc.h      |    1 +
>>> net/sunrpc/sunrpc_syms.c |    2 ++
>>> net/sunrpc/svcauth.c     |   18 ++++++++++++++++++
>>> 3 files changed, 21 insertions(+)
>>> 
>>> diff --git a/net/sunrpc/sunrpc.h b/net/sunrpc/sunrpc.h
>>> index 47a756503d11..f6fe2e6cd65a 100644
>>> --- a/net/sunrpc/sunrpc.h
>>> +++ b/net/sunrpc/sunrpc.h
>>> @@ -52,4 +52,5 @@ static inline int sock_is_loopback(struct sock *sk)
>>> 
>>> int rpc_clients_notifier_register(void);
>>> void rpc_clients_notifier_unregister(void);
>>> +void auth_domain_cleanup(void);
>>> #endif /* _NET_SUNRPC_SUNRPC_H */
>>> diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
>>> index f9edaa9174a4..236fadc4a439 100644
>>> --- a/net/sunrpc/sunrpc_syms.c
>>> +++ b/net/sunrpc/sunrpc_syms.c
>>> @@ -23,6 +23,7 @@
>>> #include <linux/sunrpc/rpc_pipe_fs.h>
>>> #include <linux/sunrpc/xprtsock.h>
>>> 
>>> +#include "sunrpc.h"
>>> #include "netns.h"
>>> 
>>> unsigned int sunrpc_net_id;
>>> @@ -131,6 +132,7 @@ cleanup_sunrpc(void)
>>>    unregister_rpc_pipefs();
>>>    rpc_destroy_mempool();
>>>    unregister_pernet_subsys(&sunrpc_net_ops);
>>> +    auth_domain_cleanup();
>>> #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
>>>    rpc_unregister_sysctl();
>>> #endif
>>> diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
>>> index 552617e3467b..477890e8b9d8 100644
>>> --- a/net/sunrpc/svcauth.c
>>> +++ b/net/sunrpc/svcauth.c
>>> @@ -205,3 +205,21 @@ struct auth_domain *auth_domain_find(char *name)
>>>    return NULL;
>>> }
>>> EXPORT_SYMBOL_GPL(auth_domain_find);
>>> +
>>> +void auth_domain_cleanup(void)
>>> +{
>>> +    /* There should be no auth_domains left at module unload */
>> 
>> Since this is a globally-visible function, could you move this comment
>> into a Doxy documenting comment before the function? It should make clear
>> that the purpose of this function is only for debugging.
> 
> I wouldn't call it "globally-visible" as it isn't exported, and isn't
> even declared in linux/include/...
> But a Doxy comment is probably justified.
> 
>> 
>> 
>>> +    int h;
>>> +    bool found = false;
>>> +
>>> +    for (h = 0; h < DN_HASHMAX; h++) {
>>> +        struct auth_domain *hp;
>>> +
>>> +        hlist_for_each_entry(hp, auth_domain_table+h, hash) {
>>> +            found = true;
>>> +            printk(KERN_WARNING "sunrpc: domain %s still present at module unload.\n",
>>> +                   hp->name);
>> 
>> Nit: Documentation/process/coding-style.rst recommends using the pr_warn()
>> macro here (and equivalents in other patches)... And note that "svc:" is
>> the conventional prefix for server-side warnings.
> 
> I'll fix that, thanks.
> 
>> 
>> I'm wondering... is it safe to release an auth_domain here if one is found,
>> so that it is not actually orphaned? The warning is information for
>> developers; there's nothing, say, an administrator can do about this
>> situation.
> 
> I don't think it is safe to release the domain.  The ->release()
> function could be in a module that has already been unloaded.

A comment to that effect would be good. Up to you!


>>> +        }
>>> +    }
>>> +    WARN(found, "sunrpc: auth_domain_table not clean -> memory leak\n");
>> 
>> Not sure a stack trace in addition to the above warning messages adds
>> relevant information. Can you provide a little justification for that?
> 
> I guess so.  I wanted a nice loud warning - and people tend to notice
> stack traces more than they notice printks - it was an attempt at human
> engineering :-)
> 
> Maybe I'll just leave it as pr_warn...
> 
> Thanks for the review.
> 
> NeilBrown
> 
> 
>> 
>> Thanks!
>> 
>> 
>>> +}
>>> 
>>> 
>> 
>> --
>> Chuck Lever

[PATCH 1/3] sunrpc: check that domain table is empty at module unload.

[NeilBrown]

The domain table should be empty at module unload.  If it isn't there is
a bug somewhere.  So check and report.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
Signed-off-by: NeilBrown <neilb@suse.de>
---
 net/sunrpc/sunrpc.h      |    1 +
 net/sunrpc/sunrpc_syms.c |    2 ++
 net/sunrpc/svcauth.c     |   25 +++++++++++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/net/sunrpc/sunrpc.h b/net/sunrpc/sunrpc.h
index 47a756503d11..f6fe2e6cd65a 100644
--- a/net/sunrpc/sunrpc.h
+++ b/net/sunrpc/sunrpc.h
@@ -52,4 +52,5 @@ static inline int sock_is_loopback(struct sock *sk)
 
 int rpc_clients_notifier_register(void);
 void rpc_clients_notifier_unregister(void);
+void auth_domain_cleanup(void);
 #endif /* _NET_SUNRPC_SUNRPC_H */
diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
index f9edaa9174a4..236fadc4a439 100644
--- a/net/sunrpc/sunrpc_syms.c
+++ b/net/sunrpc/sunrpc_syms.c
@@ -23,6 +23,7 @@
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/sunrpc/xprtsock.h>
 
+#include "sunrpc.h"
 #include "netns.h"
 
 unsigned int sunrpc_net_id;
@@ -131,6 +132,7 @@ cleanup_sunrpc(void)
 	unregister_rpc_pipefs();
 	rpc_destroy_mempool();
 	unregister_pernet_subsys(&sunrpc_net_ops);
+	auth_domain_cleanup();
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 	rpc_unregister_sysctl();
 #endif
diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
index 552617e3467b..998b196b6176 100644
--- a/net/sunrpc/svcauth.c
+++ b/net/sunrpc/svcauth.c
@@ -21,6 +21,8 @@
 
 #include <trace/events/sunrpc.h>
 
+#include "sunrpc.h"
+
 #define RPCDBG_FACILITY	RPCDBG_AUTH
 
 
@@ -205,3 +207,26 @@ struct auth_domain *auth_domain_find(char *name)
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(auth_domain_find);
+
+/**
+ * auth_domain_cleanup - check that the auth_domain table is empty
+ *
+ * On module unload the auth_domain_table must be empty.  To make it
+ * easier to catch bugs which don't clean up domains properly, we
+ * warn if anything remains in the table at cleanup time.
+ *
+ * Note that we cannot proactively remove the domains at this stage.
+ * The ->release() function might be in a module that has already been
+ * unloaded.
+ */
+
+void auth_domain_cleanup(void)
+{
+	int h;
+	struct auth_domain *hp;
+
+	for (h = 0; h < DN_HASHMAX; h++)
+		hlist_for_each_entry(hp, &auth_domain_table[h], hash)
+			pr_warn("svc: domain %s still present at module unload.\n",
+				hp->name);
+}