On Thu, 2 May 2019 14:27:04 +0200 Eugeniu Rosca erosca@de.adit-jv.com wrote:

Below is what happens on R-Car H3ULCB-KF using clean U-Boot v2019.04-00810-g6aebc0d11a10 and r8a7795_ulcb_defconfig:

=> ### interrupt autoboot => gpt verify mmc 1 No partition list provided - only basic check Verify GPT: success! => ### keep calling 'gpt verify mmc 1' => ### on 58th call, we are out of memory: => gpt verify mmc 1 alloc_read_gpt_entries: ERROR: Can't allocate 0X4000 bytes for GPT Entries GPT: Failed to allocate memory for PTE gpt_verify_headers: *** ERROR: Invalid Backup GPT *** Verify GPT: error!

This is caused by calling is_gpt_valid() twice (hence allocating pte also twice via alloc_read_gpt_entries()) while freeing pte only _once_ in the caller of gpt_verify_headers(). Fix that by freeing the pte allocated and populated for primary GPT _before_ allocating and populating the pte for backup GPT. The latter will be freed by the caller of gpt_verify_headers().

With the fix applied, the reproduction scenario [1-2] has been run hundreds of times in a loop w/o running into OOM.

[1] gpt verify mmc 1 [2] gpt verify mmc 1 $partitions

Fixes: cef68bf9042dda ("gpt: part: Definition and declaration of GPT verification functions") Signed-off-by: Eugeniu Rosca erosca@de.adit-jv.com Reviewed-by: Heinrich Schuchardt xypron.glpk@gmx.de -- v2:

• Added Reviewed-by: Heinrich Schuchardt

v1:

• https://patchwork.ozlabs.org/patch/1092943/

---

disk/part_efi.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/disk/part_efi.c b/disk/part_efi.c index 812d14cdd871..c0fa753339c8 100644 --- a/disk/part_efi.c +++ b/disk/part_efi.c @@ -698,6 +698,10 @@ int gpt_verify_headers(struct blk_desc *dev_desc, gpt_header *gpt_head, __func__); return -1; }

• /* Free pte before allocating again */
• free(*gpt_pte);
• if (is_gpt_valid(dev_desc, (dev_desc->lba - 1), gpt_head, gpt_pte) != 1) { printf("%s: *** ERROR: Invalid Backup GPT ***\n",

Reviewed-by: Lukasz Majewski lukma@denx.de

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

On Thu, 2 May 2019 14:27:05 +0200 Eugeniu Rosca erosca@de.adit-jv.com wrote:

Apply the following changes:

• Guard the 'gpt read' command by 'ifdef CONFIG_CMD_GPT_RENAME', since 'gpt read' is not available on CMD_GPT_RENAME=n
• Prefix the {read,swap,rename} commands with one space for

consistency

• Prefix the 'guid' commands with 'gpt' for consistency

Signed-off-by: Eugeniu Rosca erosca@de.adit-jv.com Reviewed-by: Heinrich Schuchardt xypron.glpk@gmx.de -- v2:

• Added Reviewed-by: Heinrich Schuchardt

v1:

• https://patchwork.ozlabs.org/patch/1092944/

---

cmd/gpt.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/cmd/gpt.c b/cmd/gpt.c index 638870352f40..33cda513969f 100644 --- a/cmd/gpt.c +++ b/cmd/gpt.c @@ -876,21 +876,21 @@ U_BOOT_CMD(gpt, CONFIG_SYS_MAXARGS, 1, do_gpt, " Example usage:\n" " gpt write mmc 0 $partitions\n" " gpt verify mmc 0 $partitions\n"

• " read <interface> <dev>\n"
• " - read GPT into a data structure for manipulation\n"
• " guid <interface> <dev>\n"

• " gpt guid <interface> <dev>\n" " - print disk GUID\n"

• " guid <interface> <dev> <varname>\n"

• " gpt guid <interface> <dev> <varname>\n" " - set environment variable to disk GUID\n" " Example usage:\n" " gpt guid mmc 0\n" " gpt guid mmc 0 varname\n"

#ifdef CONFIG_CMD_GPT_RENAME "gpt partition renaming commands:\n"

• "gpt swap <interface> <dev> <name1> <name2>\n"

• " gpt read <interface> <dev>\n"
• " - read GPT into a data structure for manipulation\n"
• " gpt swap <interface> <dev> <name1> <name2>\n" " - change all partitions named name1 to name2\n" " and vice-versa\n"

• "gpt rename <interface> <dev> <part> <name>\n"

• " gpt rename <interface> <dev> <part> <name>\n" " - rename the specified partition\n" " Example usage:\n" " gpt swap mmc 0 foo bar\n"

Reviewed-by: Lukasz Majewski lukma@denx.de

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

On 5/2/19 2:27 PM, Eugeniu Rosca wrote:

The random uuid values (enabled via CONFIG_RANDOM_UUID=y) on our platform are always the same. Below is consistent on each cold boot:

=> ### interrupt autoboot => env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc ... uuid_gpt_misc=d117f98e-6f2c-d04b-a5b2-331a19f91cb2 => env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc ... uuid_gpt_misc=ad5ec4b6-2d9f-8544-9417-fe3bd1c9b1b3 => env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc ... uuid_gpt_misc=cceb0b18-39cb-d547-9db7-03b405fa77d4 => env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc ... uuid_gpt_misc=d4981a2b-0478-544e-9607-7fd3c651068d => env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc ... uuid_gpt_misc=6d6c9a36-e919-264d-a9ee-bd00379686c7

While the uuids do change on every 'gpt write' command, the values appear to be taken from the same pool, in the same order.

Assuming U-Boot with RANDOM_UUID=y is deployed on a large number of devices, all those devices would essentially expose the same UUID, breaking the assumption of system/RFS/application designers who rely on UUID as being globally unique (e.g. a database using UUID as key would alias/mix up entries/records due to duplicated UUID).

The root cause seems to be simply _not_ seeding PRNG before generating a random value. It turns out this belongs to an established class of PRNG-specific problems, commonly known as "unseeded randomness", for which I am able to find below bugs/CVE/CWE:

• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2015-0285 ("CVE-2015-0285 openssl: handshake with unseeded PRNG")
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2015-9019 ("CVE-2015-9019 libxslt: math.random() in xslt uses unseeded randomness")
• https://cwe.mitre.org/data/definitions/336.html ("CWE-336: Same Seed in Pseudo-Random Number Generator (PRNG)")

The first revision [1] of this patch updated the seed based on the output of get_timer(), similar to [4].

There are two problems with this approach:

• get_timer() has a poor _ms_ resolution
• when gen_rand_uuid() is called in a loop, get_timer() returns the same result, leading to the same seed being passed to srand(), leading to the same uuid being generated for several partitions with different names

The above drawbacks have been addressed in the second version [2]. In its third revision (current), the patch reworded the description and summary line to emphasize it is a *fix* rather than an improvement.

Testing [3] consisted of running 'gpt write mmc 1 $partitions' in a loop on R-Car3 for several minutes, collecting 8844 randomly generated UUIDS. Two consecutive cold boots are concatenated in the log. As a result, all uuid values are unique (scripted check).

Thanks to Roman, who reported the issue and provided support in fixing.

[1] https://patchwork.ozlabs.org/patch/1091802/ [2] https://patchwork.ozlabs.org/patch/1092945/ [3] https://gist.github.com/erosca/2820be9d554f76b982edd48474d0e7ca [4] commit da384a9d7628 ("net: rename and refactor eth_rand_ethaddr() function")

Reported-by: Roman Stratiienko roman.stratiienko@globallogic.com Signed-off-by: Eugeniu Rosca erosca@de.adit-jv.com

Reviewed-by: Heinrich Schuchardt xypron.glpk@gmx.de

-- v3:

• Reworked the patch summary line and description to emphasize this is a fix rather than an improvement by precisely pointing out the root cause and mentioning related CVE/CWE.

v2:

• https://patchwork.ozlabs.org/patch/1092945/
• Replaced get_timer(0) with get_ticks() and added rand() to seed value
• Performed extensive testing on R-Car3 (ARMv8). See: https://gist.github.com/erosca/2820be9d554f76b982edd48474d0e7ca

v1:

• https://patchwork.ozlabs.org/patch/1092944/

---

lib/uuid.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/lib/uuid.c b/lib/uuid.c index fa20ee39fc32..2d4d6ef7e461 100644 --- a/lib/uuid.c +++ b/lib/uuid.c @@ -238,6 +238,8 @@ void gen_rand_uuid(unsigned char *uuid_bin) unsigned int *ptr = (unsigned int *)&uuid; int i;

• srand(get_ticks() + rand());
• /* Set all fields randomly */ for (i = 0; i < sizeof(struct uuid) / sizeof(*ptr); i++) *(ptr + i) = cpu_to_be32(rand());