[PATCH v1 1/1] sysctl: introduce uuid_le and uuid_be

[PATCH v1 1/1] sysctl: introduce uuid_le and uuid_be

[Andy Shevchenko]

By default the sysctl interface returns random UUID in big endian format.
Sometimes it's not suitable, e.g. using generated UUID for EFI variable name.
Provide uuid_le and uuid_be to comprehence that interface.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/char/random.c       | 44 +++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/sysctl.h |  4 +++-
 kernel/sysctl_binary.c      | 48 ++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 94 insertions(+), 2 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0158d3b..a864013 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1673,6 +1673,38 @@ static int proc_do_uuid(struct ctl_table *table, int write,
 	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
 }
 
+static int proc_do_uuid_le(struct ctl_table *table, int write,
+			   void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table fake_table;
+	unsigned char buf[64];
+	uuid_le uuid;
+
+	uuid_le_gen(&uuid);
+	sprintf(buf, "%pUl", &uuid);
+
+	fake_table.data = buf;
+	fake_table.maxlen = sizeof(buf);
+
+	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
+}
+
+static int proc_do_uuid_be(struct ctl_table *table, int write,
+			   void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table fake_table;
+	unsigned char buf[64];
+	uuid_be uuid;
+
+	uuid_be_gen(&uuid);
+	sprintf(buf, "%pUb", &uuid);
+
+	fake_table.data = buf;
+	fake_table.maxlen = sizeof(buf);
+
+	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
+}
+
 /*
  * Return entropy available scaled to integral bits
  */
@@ -1745,6 +1777,18 @@ struct ctl_table random_table[] = {
 		.mode		= 0444,
 		.proc_handler	= proc_do_uuid,
 	},
+	{
+		.procname	= "uuid_le",
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= proc_do_uuid_le,
+	},
+	{
+		.procname	= "uuid_be",
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= proc_do_uuid_be,
+	},
 #ifdef ADD_INTERRUPT_BENCH
 	{
 		.procname	= "add_interrupt_avg_cycles",
diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index 0956373..db5fcf1 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -233,7 +233,9 @@ enum
 	RANDOM_READ_THRESH=3,
 	RANDOM_WRITE_THRESH=4,
 	RANDOM_BOOT_ID=5,
-	RANDOM_UUID=6
+	RANDOM_UUID=6,
+	RANDOM_UUID_LE=7,
+	RANDOM_UUID_BE=8,
 };
 
 /* /proc/sys/kernel/pty */
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 6eb99c1..56b8c90 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -28,6 +28,8 @@ static bin_convert_t bin_string;
 static bin_convert_t bin_intvec;
 static bin_convert_t bin_ulongvec;
 static bin_convert_t bin_uuid;
+static bin_convert_t bin_uuid_le;
+static bin_convert_t bin_uuid_be;
 static bin_convert_t bin_dn_node_address;
 
 #define CTL_DIR   bin_dir
@@ -35,6 +37,8 @@ static bin_convert_t bin_dn_node_address;
 #define CTL_INT   bin_intvec
 #define CTL_ULONG bin_ulongvec
 #define CTL_UUID  bin_uuid
+#define CTL_UUID_LE  bin_uuid_le
+#define CTL_UUID_BE  bin_uuid_be
 #define CTL_DNADR bin_dn_node_address
 
 #define BUFSZ 256
@@ -53,6 +57,8 @@ static const struct bin_table bin_random_table[] = {
 	{ CTL_INT,	RANDOM_WRITE_THRESH,	"write_wakeup_threshold" },
 	{ CTL_UUID,	RANDOM_BOOT_ID,		"boot_id" },
 	{ CTL_UUID,	RANDOM_UUID,		"uuid" },
+	{ CTL_UUID_LE,	RANDOM_UUID_LE,		"uuid_le" },
+	{ CTL_UUID_BE,	RANDOM_UUID_BE,		"uuid_be" },
 	{}
 };
 
@@ -1111,7 +1117,7 @@ out:
 	return result;
 }
 
-static ssize_t bin_uuid(struct file *file,
+static ssize_t bin_uuid_be(struct file *file,
 	void __user *oldval, size_t oldlen, void __user *newval, size_t newlen)
 {
 	ssize_t result, copied = 0;
@@ -1145,6 +1151,46 @@ out:
 	return result;
 }
 
+static ssize_t bin_uuid_le(struct file *file,
+	void __user *oldval, size_t oldlen, void __user *newval, size_t newlen)
+{
+	ssize_t result, copied = 0;
+
+	/* Only supports reads */
+	if (oldval && oldlen) {
+		char buf[UUID_STRING_LEN + 1];
+		uuid_le uuid;
+
+		result = kernel_read(file, 0, buf, sizeof(buf) - 1);
+		if (result < 0)
+			goto out;
+
+		buf[result] = '\0';
+
+		result = -EIO;
+		if (uuid_le_to_bin(buf, &uuid))
+			goto out;
+
+		if (oldlen > 16)
+			oldlen = 16;
+
+		result = -EFAULT;
+		if (copy_to_user(oldval, &uuid, oldlen))
+			goto out;
+
+		copied = oldlen;
+	}
+	result = copied;
+out:
+	return result;
+}
+
+static ssize_t bin_uuid(struct file *file,
+	void __user *oldval, size_t oldlen, void __user *newval, size_t newlen)
+{
+	return bin_uuid_be(file, oldval, oldlen, newval, newlen);
+}
+
 static ssize_t bin_dn_node_address(struct file *file,
 	void __user *oldval, size_t oldlen, void __user *newval, size_t newlen)
 {
-- 
2.8.1

Re: [PATCH v1 1/1] sysctl: introduce uuid_le and uuid_be

[Andrew Morton]

On Tue, 24 May 2016 20:27:27 +0300 Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> By default the sysctl interface returns random UUID in big endian format.
> Sometimes it's not suitable, e.g. using generated UUID for EFI variable name.
> Provide uuid_le and uuid_be to comprehence that interface.
> 
> ...
>
>  drivers/char/random.c       | 44 +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/sysctl.h |  4 +++-
>  kernel/sysctl_binary.c      | 48 ++++++++++++++++++++++++++++++++++++++++++++

Why does the kernel need to do this?  If userspace wants a random uuid
then it can grab a random number and cook up the UUID itself.

Re: [PATCH v1 1/1] sysctl: introduce uuid_le and uuid_be

[Andy Shevchenko]

On Tue, 2016-05-24 at 13:15 -0700, Andrew Morton wrote:
> On Tue, 24 May 2016 20:27:27 +0300 Andy Shevchenko <andriy.shevchenko@
> linux.intel.com> wrote:
> 
> > By default the sysctl interface returns random UUID in big endian
> > format.
> > Sometimes it's not suitable, e.g. using generated UUID for EFI
> > variable name.
> > Provide uuid_le and uuid_be to comprehence that interface.
> > 
> > ...
> > 
> >  drivers/char/random.c       | 44
> > +++++++++++++++++++++++++++++++++++++++++
> >  include/uapi/linux/sysctl.h |  4 +++-
> >  kernel/sysctl_binary.c      | 48
> > ++++++++++++++++++++++++++++++++++++++++++++
> 
> Why does the kernel need to do this?  If userspace wants a random uuid
> then it can grab a random number and cook up the UUID itself.

Good question. I dunno why we have uuid in the first place there. At
some point I noticed people who recommend to use that file to get a
random UUID(s), but apparently they don't aware that endianess matters. 

P.S. I thought to send this as RFC, but decided to drop the notation in
last minute. So, it's okay to drop it.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

Re: [PATCH v1 1/1] sysctl: introduce uuid_le and uuid_be

[Theodore Ts'o]

I'm also curious what !@#!? idiot came up with the concept of Little
Endian UUID's.  UUID's, and how to transform them from a printed
representation to a binary presentation, were well defined in a very
specific way in RFC-4122, which came from HP's Apollo/Domain OS, and
was adopted by the OSF/DCE, as well as later by Microsoft.  In all
cases, there was never any such thing as little endian versus big
endian UUID's.  Might as well talk about big-endian and little endian
IP addresses.  This way lies madness.

It's also the case that if all you need is a random UUID's, that
*technically* the endianness matters, but in actual practice, it
really won't matter.

					- Ted

P.S.  Let me guess, it was some clueless Intel engineer when they were
drafting the EFI spec?  Sigh....