[PATCH 0/2] Fix /proc/sys/fs/nfs/nsm_use_hostnames on big endian machines

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9 messages, 5 authors, 2021-09-16 · open the first message on its own page

[PATCH 0/2] Fix /proc/sys/fs/nfs/nsm_use_hostnames on big endian machines

From: Thomas Huth <hidden>
Date: 2021-08-03 10:59:53

There is an endianess problem with /proc/sys/fs/nfs/nsm_use_hostnames
(which can e.g. be seen on an s390x host) :

 # modprobe lockd nsm_use_hostnames=1
 # cat /proc/sys/fs/nfs/nsm_use_hostnames
 16777216

The nsm_use_hostnames variable is declared as "bool" which is required
for the correct type for the module parameter. However, this does not
work correctly with the entry in the /proc filesystem since this
currently requires "int".

Jia He already provided patches for this problem a couple of years ago,
but apparently they felt through the cracks and never got merged. So
here's a rebased version to finally fix this issue.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1764075

Jia He (2):
  sysctl: introduce new proc handler proc_dobool
  lockd: change the proc_handler for nsm_use_hostnames

 fs/lockd/svc.c         |  2 +-
 include/linux/sysctl.h |  2 ++
 kernel/sysctl.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

-- 
2.27.0

[PATCH 1/2] sysctl: introduce new proc handler proc_dobool

From: Thomas Huth <hidden>
Date: 2021-08-03 10:59:55

From: Jia He <redacted>

This is to let bool variable could be correctly displayed in
big/little endian sysctl procfs. sizeof(bool) is arch dependent,
proc_dobool should work in all arches.

Suggested-by: Pan Xinhui <redacted>
Signed-off-by: Jia He <redacted>
[thuth: rebased the patch to the current kernel version]
Signed-off-by: Thomas Huth <redacted>
---
 include/linux/sysctl.h |  2 ++
 kernel/sysctl.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index d99ca99837de..1fa2b69c6fc3 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -48,6 +48,8 @@ typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
 
 int proc_dostring(struct ctl_table *, int, void *, size_t *, loff_t *);
+int proc_dobool(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos);
 int proc_dointvec(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 272f4a272f8c..25e49b4d8049 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -536,6 +536,21 @@ static void proc_put_char(void **buf, size_t *size, char c)
 	}
 }
 
+static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
+				int *valp,
+				int write, void *data)
+{
+	if (write) {
+		*(bool *)valp = *lvalp;
+	} else {
+		int val = *(bool *)valp;
+
+		*lvalp = (unsigned long)val;
+		*negp = false;
+	}
+	return 0;
+}
+
 static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
 				 int *valp,
 				 int write, void *data)
@@ -798,6 +813,26 @@ static int do_proc_douintvec(struct ctl_table *table, int write,
 				   buffer, lenp, ppos, conv, data);
 }
 
+/**
+ * proc_dobool - read/write a bool
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
+ * values from/to the user buffer, treated as an ASCII string.
+ *
+ * Returns 0 on success.
+ */
+int proc_dobool(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
+{
+	return do_proc_dointvec(table, write, buffer, lenp, ppos,
+				do_proc_dobool_conv, NULL);
+}
+
 /**
  * proc_dointvec - read a vector of integers
  * @table: the sysctl table
@@ -1630,6 +1665,12 @@ int proc_dostring(struct ctl_table *table, int write,
 	return -ENOSYS;
 }
 
+int proc_dobool(struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	return -ENOSYS;
+}
+
 int proc_dointvec(struct ctl_table *table, int write,
 		  void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -3425,6 +3466,7 @@ int __init sysctl_init(void)
  * No sense putting this after each symbol definition, twice,
  * exception granted :-)
  */
+EXPORT_SYMBOL(proc_dobool);
 EXPORT_SYMBOL(proc_dointvec);
 EXPORT_SYMBOL(proc_douintvec);
 EXPORT_SYMBOL(proc_dointvec_jiffies);
-- 
2.27.0

[PATCH 2/2] lockd: change the proc_handler for nsm_use_hostnames

From: Thomas Huth <hidden>
Date: 2021-08-03 11:00:00

From: Jia He <redacted>

nsm_use_hostnames is a module parameter and it will be exported to sysctl
procfs. This is to let user sometimes change it from userspace. But the
minimal unit for sysctl procfs read/write it sizeof(int).
In big endian system, the converting from/to  bool to/from int will cause
error for proc items.

This patch use a new proc_handler proc_dobool to fix it.

Signed-off-by: Jia He <redacted>
Reviewed-by: Pan Xinhui <redacted>
[thuth: Fix typo in commit message]
Signed-off-by: Thomas Huth <redacted>
---
 fs/lockd/svc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 2de048f80eb8..0ab9756ed235 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -584,7 +584,7 @@ static struct ctl_table nlm_sysctls[] = {
 		.data		= &nsm_use_hostnames,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dobool,
 	},
 	{
 		.procname	= "nsm_local_state",
-- 
2.27.0

Re: [PATCH 0/2] Fix /proc/sys/fs/nfs/nsm_use_hostnames on big endian machines

From: J. Bruce Fields <hidden>
Date: 2021-08-03 14:08:50

Looks good to me.  Could Chuck take it with nfsd stuff if somebody could
ACK the sysctl part?

--b.

On Tue, Aug 03, 2021 at 12:59:35PM +0200, Thomas Huth wrote:
There is an endianess problem with /proc/sys/fs/nfs/nsm_use_hostnames
(which can e.g. be seen on an s390x host) :

 # modprobe lockd nsm_use_hostnames=1
 # cat /proc/sys/fs/nfs/nsm_use_hostnames
 16777216

The nsm_use_hostnames variable is declared as "bool" which is required
for the correct type for the module parameter. However, this does not
work correctly with the entry in the /proc filesystem since this
currently requires "int".

Jia He already provided patches for this problem a couple of years ago,
but apparently they felt through the cracks and never got merged. So
here's a rebased version to finally fix this issue.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1764075

Jia He (2):
  sysctl: introduce new proc handler proc_dobool
  lockd: change the proc_handler for nsm_use_hostnames

 fs/lockd/svc.c         |  2 +-
 include/linux/sysctl.h |  2 ++
 kernel/sysctl.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

-- 
2.27.0

Re: [PATCH 0/2] Fix /proc/sys/fs/nfs/nsm_use_hostnames on big endian machines

From: Chuck Lever III <hidden>
Date: 2021-08-03 14:24:21

Thanks for your review, Bruce. I'll watch for the additional Ack.
On Aug 3, 2021, at 10:08 AM, J. Bruce Fields [off-list ref] wrote:

Looks good to me.  Could Chuck take it with nfsd stuff if somebody could
ACK the sysctl part?

--b.

On Tue, Aug 03, 2021 at 12:59:35PM +0200, Thomas Huth wrote:
quoted
There is an endianess problem with /proc/sys/fs/nfs/nsm_use_hostnames
(which can e.g. be seen on an s390x host) :

# modprobe lockd nsm_use_hostnames=1
# cat /proc/sys/fs/nfs/nsm_use_hostnames
16777216

The nsm_use_hostnames variable is declared as "bool" which is required
for the correct type for the module parameter. However, this does not
work correctly with the entry in the /proc filesystem since this
currently requires "int".

Jia He already provided patches for this problem a couple of years ago,
but apparently they felt through the cracks and never got merged. So
here's a rebased version to finally fix this issue.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1764075

Jia He (2):
 sysctl: introduce new proc handler proc_dobool
 lockd: change the proc_handler for nsm_use_hostnames

fs/lockd/svc.c         |  2 +-
include/linux/sysctl.h |  2 ++
kernel/sysctl.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 1 deletion(-)

-- 
2.27.0
--
Chuck Lever


Re: [PATCH 0/2] Fix /proc/sys/fs/nfs/nsm_use_hostnames on big endian machines

From: Jia He <hidden>
Date: 2021-08-04 02:13:15

On 2021/8/3 18:59, Thomas Huth wrote:
There is an endianess problem with /proc/sys/fs/nfs/nsm_use_hostnames
(which can e.g. be seen on an s390x host) :

  # modprobe lockd nsm_use_hostnames=1
  # cat /proc/sys/fs/nfs/nsm_use_hostnames
  16777216

The nsm_use_hostnames variable is declared as "bool" which is required
for the correct type for the module parameter. However, this does not
work correctly with the entry in the /proc filesystem since this
currently requires "int".

Jia He already provided patches for this problem a couple of years ago,
but apparently they felt through the cracks and never got merged. So
here's a rebased version to finally fix this issue.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1764075

Jia He (2):
   sysctl: introduce new proc handler proc_dobool
   lockd: change the proc_handler for nsm_use_hostnames
Thanks for picking them up ;-)

---
Cheers,
Justin (Jia He)

Re: [PATCH 0/2] Fix /proc/sys/fs/nfs/nsm_use_hostnames on big endian machines

From: Chuck Lever III <hidden>
Date: 2021-08-09 17:50:45

On Aug 3, 2021, at 6:59 AM, Thomas Huth [off-list ref] wrote:

There is an endianess problem with /proc/sys/fs/nfs/nsm_use_hostnames
(which can e.g. be seen on an s390x host) :

# modprobe lockd nsm_use_hostnames=1
# cat /proc/sys/fs/nfs/nsm_use_hostnames
16777216

The nsm_use_hostnames variable is declared as "bool" which is required
for the correct type for the module parameter. However, this does not
work correctly with the entry in the /proc filesystem since this
currently requires "int".

Jia He already provided patches for this problem a couple of years ago,
but apparently they felt through the cracks and never got merged. So
here's a rebased version to finally fix this issue.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1764075

Jia He (2):
 sysctl: introduce new proc handler proc_dobool
 lockd: change the proc_handler for nsm_use_hostnames

fs/lockd/svc.c         |  2 +-
include/linux/sysctl.h |  2 ++
kernel/sysctl.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 1 deletion(-)

-- 
2.27.0
To get these patches in front of our zero-day apparatus,
I've applied them to the for-next topic branch here:

https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git/log/?h=for-next

However I haven't seen an Ack for the kernel/sysctl.c change yet.


--
Chuck Lever


Re: [PATCH 1/2] sysctl: introduce new proc handler proc_dobool

From: Kees Cook <hidden>
Date: 2021-09-16 22:03:24

On Tue, Aug 03, 2021 at 12:59:36PM +0200, Thomas Huth wrote:
From: Jia He <redacted>

This is to let bool variable could be correctly displayed in
big/little endian sysctl procfs. sizeof(bool) is arch dependent,
proc_dobool should work in all arches.

Suggested-by: Pan Xinhui <redacted>
Signed-off-by: Jia He <redacted>
Hi! I apologize for the delay. Yes, this looks good to me; thanks!

Acked-by: Kees Cook <redacted>

-- 
Kees Cook

Re: [PATCH 2/2] lockd: change the proc_handler for nsm_use_hostnames

From: Kees Cook <hidden>
Date: 2021-09-16 22:05:24

On Tue, Aug 03, 2021 at 12:59:37PM +0200, Thomas Huth wrote:
quoted hunk
From: Jia He <redacted>

nsm_use_hostnames is a module parameter and it will be exported to sysctl
procfs. This is to let user sometimes change it from userspace. But the
minimal unit for sysctl procfs read/write it sizeof(int).
In big endian system, the converting from/to  bool to/from int will cause
error for proc items.

This patch use a new proc_handler proc_dobool to fix it.

Signed-off-by: Jia He <redacted>
Reviewed-by: Pan Xinhui <redacted>
[thuth: Fix typo in commit message]
Signed-off-by: Thomas Huth <redacted>
---
 fs/lockd/svc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 2de048f80eb8..0ab9756ed235 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -584,7 +584,7 @@ static struct ctl_table nlm_sysctls[] = {
 		.data		= &nsm_use_hostnames,
 		.maxlen		= sizeof(int),
For robustness, maybe this should be:

		.maxlen		= sizeof(nsm_use_hostnames),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dobool,
 	},
 	{
 		.procname	= "nsm_local_state",
-- 
2.27.0
Reviewed-by: Kees Cook <redacted>

Also, I wonder what other BE-corrupted bools are out there?

-- 
Kees Cook
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