1. photon
  2. Commit d11e2874af8162fcb29763d4f106772a363c5eb0
Browse code

kernels: Improve error-handling of rdrand-rng kernel driver

Improve the rdrand-rng driver to be robust in the face of various
errors and edge cases. Specifically,

- arch_get_random_long() and arch_get_random_seed_long() can fail.
Check their return values to deal with this appropriately.

- The number of random bytes requested can be arbitrary; so fill in
the supplied buffer carefully.

- Prefer rdseed over rdrand whenever possible.

Thanks to Joao Lima and Lonnie Abelbeck (@abelbeck) for suggesting
some of these improvements.

Change-Id: I4612215c3f4c66d216c875cea7ae09ab6aedaace
Reviewed-on: http://photon-jenkins.eng.vmware.com:8082/5841
Tested-by: gerrit-photon <photon-checkins@vmware.com>
Reviewed-by: Srinidhi Rao <srinidhir@vmware.com>
Reviewed-by: Srivatsa S. Bhat <srivatsab@vmware.com>

Srivatsa S. Bhat authored on 2018/10/03 07:21:20
Showing 5 changed files
SPECS/linux/0001-hwrng-rdrand-Add-RNG-driver-based-on-x86-rdrand-inst.patch
History View file @ d11e287
... ... 
@@ -12,14 +12,15 @@ entropy-starved virtual machines.
12 12
13 13 
 Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
14 14 
 ---
15 
- drivers/char/hw_random/Kconfig      | 14 +++++++++
15 
+
16 
+ drivers/char/hw_random/Kconfig      | 14 ++++++++
16 17 
  drivers/char/hw_random/Makefile     |  1 +
17 
- drivers/char/hw_random/rdrand-rng.c | 61 +++++++++++++++++++++++++++++++++++++
18 
- 3 files changed, 76 insertions(+)
18 
+ drivers/char/hw_random/rdrand-rng.c | 72 +++++++++++++++++++++++++++++++++++++
19 
+ 3 files changed, 87 insertions(+)
19 20 
  create mode 100644 drivers/char/hw_random/rdrand-rng.c
20 21
21 22 
 diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
22 
-index 200dab5..cc3a67d 100644
23 
+index 200dab5..8b6d236 100644
23 24 
 --- a/drivers/char/hw_random/Kconfig
24 25 
 +++ b/drivers/char/hw_random/Kconfig
25 26 
 @@ -62,6 +62,20 @@ config HW_RANDOM_AMD
... ... 
@@ -32,7 +33,7 @@ index 200dab5..cc3a67d 100644
32 32 
 +	default HW_RANDOM
33 33 
 +	---help---
34 34 
 +	  This driver provides kernel-side support for a Random Number
35 
-+	  Generator that uses the 'rdrand' instruction on modern Intel
35 
++	  Generator that uses the RDRAND/RDSEED instructions on modern Intel
36 36 
 +	  and AMD CPUs.
37 37 
 +
38 38 
 +	  To compile this driver as a module, choose M here: the
... ... 
@@ -57,13 +58,13 @@ index 5f52b1e..5b92c8e 100644
57 57 
  obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o
58 58 
 diff --git a/drivers/char/hw_random/rdrand-rng.c b/drivers/char/hw_random/rdrand-rng.c
59 59 
 new file mode 100644
60 
-index 0000000..e1cf7f3
60 
+index 0000000..ba017f3
61 61 
 --- /dev/null
62 62 
 +++ b/drivers/char/hw_random/rdrand-rng.c
63 
-@@ -0,0 +1,61 @@
63 
+@@ -0,0 +1,72 @@
64 64 
 +// SPDX-License-Identifier: GPL-2.0
65 65 
 +/*
66 
-+ * RNG driver that uses the 'rdrand' instruction (found on modern
66 
++ * RNG driver that uses the RDRAND/RDSEED instructions (found on modern
67 67 
 + * Intel and AMD CPUs).
68 68 
 + *
69 69 
 + * Author: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
... ... 
@@ -77,18 +78,27 @@ index 0000000..e1cf7f3
77 77 
 +
78 78 
 +#define PFX	KBUILD_MODNAME ": "
79 79 
 +
80 
-+static int rdrand_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
80 
++static int rdrand_rng_read(struct hwrng *rng, void *buf, size_t max_bytes, bool wait)
81 81 
 +{
82 
-+	unsigned long *data = buf;
83 
-+	size_t read = 0;
84 
-+
85 
-+	while (read < max) {
86 
-+		arch_get_random_long(data);
87 
-+		data++;
88 
-+		read += sizeof(unsigned long);
82 
++	char *p = buf;
83 
++	size_t read_bytes = 0;
84 
++
85 
++	while (max_bytes) {
86 
++		unsigned long v;
87 
++		size_t chunk = min(max_bytes, (int)sizeof(unsigned long));
88 
++
89 
++		if (unlikely(!arch_get_random_seed_long(&v)) &&
90 
++		    unlikely(!arch_get_random_long(&v))) {
91 
++			break;
92 
++		}
93 
++
94 
++		memcpy(p, &v, chunk);
95 
++		p += chunk;
96 
++		max_bytes -= chunk;
97 
++		read_bytes += chunk;
89 98 
 +	}
90 99 
 +
91 
-+	return read;
100 
++	return read_bytes;
92 101 
 +}
93 102 
 +
94 103 
 +static struct hwrng rdrand_rng = {
... ... 
@@ -101,8 +111,10 @@ index 0000000..e1cf7f3
101 101 
 +{
102 102 
 +	int err = -ENODEV;
103 103 
 +
104 
-+	if (!arch_has_random())
105 
-+		return err; /* rdrand not available. */
104 
++	if (!arch_has_random_seed() && !arch_has_random()) {
105 
++		pr_err(PFX "Neither RDSEED nor RDRAND is available.\n");
106 
++		return err;
107 
++	}
106 108 
 +
107 109 
 +	err = hwrng_register(&rdrand_rng);
108 110 
 +	if (err)
... ... 
@@ -120,7 +132,7 @@ index 0000000..e1cf7f3
120 120 
 +module_exit(mod_exit);
121 121 
 +
122 122 
 +MODULE_AUTHOR("Srivatsa S. Bhat <srivatsa@csail.mit.edu>");
123 
-+MODULE_DESCRIPTION("H/W RNG driver for x86 CPUs that support rdrand");
123 
++MODULE_DESCRIPTION("H/W RNG driver for x86 CPUs that support RDRAND/RDSEED");
124 124 
 +MODULE_LICENSE("GPL");
125 125 
 --
126 126 
 2.7.4
SPECS/linux/linux-aws.spec
History View file @ d11e287
... ... 
@@ -2,7 +2,7 @@
2 2 
 Summary:        Kernel
3 3 
 Name:           linux-aws
4 4 
 Version:        4.9.130
5 
-Release:        1%{?kat_build:.%kat_build}%{?dist}
5 
+Release:        2%{?kat_build:.%kat_build}%{?dist}
6 6 
 License:    	GPLv2
7 7 
 URL:        	http://www.kernel.org/
8 8 
 Group:        	System Environment/Kernel
... ... 
@@ -443,6 +443,8 @@ ln -sf %{name}-%{uname_r}.cfg /boot/photon.cfg
443 443 
 /usr/share/doc/*
444 444
445 445 
 %changelog
446 
+*   Tue Oct 02 2018 Srivatsa S. Bhat <srivatsa@csail.mit.edu> 4.9.130-2
447 
+-   Improve error-handling of rdrand-rng kernel driver.
446 448 
 *   Mon Oct 01 2018 srinidhira0 <srinidhir@vmware.com> 4.9.130-1
447 449 
 -   Update to version 4.9.130
448 450 
 *   Mon Sep 10 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.124-2
... ... 
@@ -461,7 +463,7 @@ ln -sf %{name}-%{uname_r}.cfg /boot/photon.cfg
461 461 
 -   Update to version 4.9.114
462 462 
 *   Thu Jul 19 2018 Srivatsa S. Bhat <srivatsa@csail.mit.edu> 4.9.111-5
463 463 
 -   Apply out-of-tree patches needed for AppArmor.
464 
-*   Thu Jul 17 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-4
464 
+*   Tue Jul 17 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-4
465 465 
 -   Fix CVE-2018-10322
466 466 
 *   Thu Jul 12 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-3
467 467 
 -   Fix CVE-2017-18232, CVE-2017-18249 and CVE-2018-10323
SPECS/linux/linux-esx.spec
History View file @ d11e287
... ... 
@@ -2,7 +2,7 @@
2 2 
 Summary:        Kernel
3 3 
 Name:           linux-esx
4 4 
 Version:        4.9.130
5 
-Release:        1%{?dist}
5 
+Release:        2%{?dist}
6 6 
 License:        GPLv2
7 7 
 URL:            http://www.kernel.org/
8 8 
 Group:          System Environment/Kernel
... ... 
@@ -236,6 +236,8 @@ ln -sf linux-%{uname_r}.cfg /boot/photon.cfg
236 236 
 /usr/src/linux-headers-%{uname_r}
237 237
238 238 
 %changelog
239 
+*   Tue Oct 02 2018 Srivatsa S. Bhat <srivatsa@csail.mit.edu> 4.9.130-2
240 
+-   Improve error-handling of rdrand-rng kernel driver.
239 241 
 *   Mon Oct 01 2018 srinidhira0 <srinidhir@vmware.com> 4.9.130-1
240 242 
 -   Update to version 4.9.130
241 243 
 *   Mon Sep 10 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.124-2
... ... 
@@ -252,7 +254,7 @@ ln -sf linux-%{uname_r}.cfg /boot/photon.cfg
252 252 
 -   Update to version 4.9.116 and clear stack on fork.
253 253 
 *   Mon Jul 23 2018 srinidhira0 <srinidhir@vmware.com> 4.9.114-1
254 254 
 -   Update to version 4.9.114
255 
-*   Thu Jul 17 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-3
255 
+*   Tue Jul 17 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-3
256 256 
 -   Fix CVE-2018-10322
257 257 
 *   Thu Jul 12 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-2
258 258 
 -   Fix CVE-2017-18232, CVE-2017-18249 and CVE-2018-10323
SPECS/linux/linux-secure.spec
History View file @ d11e287
... ... 
@@ -2,7 +2,7 @@
2 2 
 Summary:        Kernel
3 3 
 Name:           linux-secure
4 4 
 Version:        4.9.130
5 
-Release:        1%{?kat_build:.%kat_build}%{?dist}
5 
+Release:        2%{?kat_build:.%kat_build}%{?dist}
6 6 
 License:        GPLv2
7 7 
 URL:            http://www.kernel.org/
8 8 
 Group:          System Environment/Kernel
... ... 
@@ -334,6 +334,8 @@ ln -sf linux-%{uname_r}.cfg /boot/photon.cfg
334 334 
 /usr/src/linux-headers-%{uname_r}
335 335
336 336 
 %changelog
337 
+*   Tue Oct 02 2018 Srivatsa S. Bhat <srivatsa@csail.mit.edu> 4.9.130-2
338 
+-   Improve error-handling of rdrand-rng kernel driver.
337 339 
 *   Mon Oct 01 2018 srinidhira0 <srinidhir@vmware.com> 4.9.130-1
338 340 
 -   Update to version 4.9.130
339 341 
 *   Mon Sep 10 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.124-2
... ... 
@@ -352,7 +354,7 @@ ln -sf linux-%{uname_r}.cfg /boot/photon.cfg
352 352 
 -   Update to version 4.9.114
353 353 
 *   Thu Jul 19 2018 Srivatsa S. Bhat <srivatsa@csail.mit.edu> 4.9.111-4
354 354 
 -   Apply out-of-tree patches needed for AppArmor.
355 
-*   Thu Jul 17 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-3
355 
+*   Tue Jul 17 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-3
356 356 
 -   Fix CVE-2018-10322
357 357 
 *   Thu Jul 12 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.111-2
358 358 
 -   Fix CVE-2017-18232, CVE-2017-18249 and CVE-2018-10323
SPECS/linux/linux.spec
History View file @ d11e287
... ... 
@@ -2,7 +2,7 @@
2 2 
 Summary:        Kernel
3 3 
 Name:           linux
4 4 
 Version:        4.9.130
5 
-Release:        1%{?kat_build:.%kat_build}%{?dist}
5 
+Release:        2%{?kat_build:.%kat_build}%{?dist}
6 6 
 License:    	GPLv2
7 7 
 URL:        	http://www.kernel.org/
8 8 
 Group:        	System Environment/Kernel
... ... 
@@ -366,6 +366,8 @@ ln -sf %{name}-%{uname_r}.cfg /boot/photon.cfg
366 366 
 /usr/share/doc/*
367 367
368 368 
 %changelog
369 
+*   Tue Oct 02 2018 Srivatsa S. Bhat <srivatsa@csail.mit.edu> 4.9.130-2
370 
+-   Improve error-handling of rdrand-rng kernel driver.
369 371 
 *   Mon Oct 01 2018 srinidhira0 <srinidhir@vmware.com> 4.9.130-1
370 372 
 -   Update to version 4.9.130
371 373 
 *   Mon Sep 10 2018 Srinidhi Rao <srinidhir@vmware.com> 4.9.124-2