user/sven/linux.git/drivers/char, branch v5.18.6

random: credit cpu and bootloader seeds by default

2022-06-22T12:27:55Z

[ Upstream commit 846bb97e131d7938847963cca00657c995b1fce1 ] This commit changes the default Kconfig values of RANDOM_TRUST_CPU and RANDOM_TRUST_BOOTLOADER to be Y by default. It does not change any existing configs or change any kernel behavior. The reason for this is several fold. As background, I recently had an email thread with the kernel maintainers of Fedora/RHEL, Debian, Ubuntu, Gentoo, Arch, NixOS, Alpine, SUSE, and Void as recipients. I noted that some distros trust RDRAND, some trust EFI, and some trust both, and I asked why or why not. There wasn't really much of a "debate" but rather an interesting discussion of what the historical reasons have been for this, and it came up that some distros just missed the introduction of the bootloader Kconfig knob, while another didn't want to enable it until there was a boot time switch to turn it off for more concerned users (which has since been added). The result of the rather uneventful discussion is that every major Linux distro enables these two options by default. While I didn't have really too strong of an opinion going into this thread -- and I mostly wanted to learn what the distros' thinking was one way or another -- ultimately I think their choice was a decent enough one for a default option (which can be disabled at boot time). I'll try to summarize the pros and cons: Pros: - The RNG machinery gets initialized super quickly, and there's no messing around with subsequent blocking behavior. - The bootloader mechanism is used by kexec in order for the prior kernel to initialize the RNG of the next kernel, which increases the entropy available to early boot daemons of the next kernel. - Previous objections related to backdoors centered around Dual_EC_DRBG-like kleptographic systems, in which observing some amount of the output stream enables an adversary holding the right key to determine the entire output stream. This used to be a partially justified concern, because RDRAND output was mixed into the output stream in varying ways, some of which may have lacked pre-image resistance (e.g. XOR or an LFSR). But this is no longer the case. Now, all usage of RDRAND and bootloader seeds go through a cryptographic hash function. This means that the CPU would have to compute a hash pre-image, which is not considered to be feasible (otherwise the hash function would be terribly broken). - More generally, if the CPU is backdoored, the RNG is probably not the realistic vector of choice for an attacker. - These CPU or bootloader seeds are far from being the only source of entropy. Rather, there is generally a pretty huge amount of entropy, not all of which is credited, especially on CPUs that support instructions like RDRAND. In other words, assuming RDRAND outputs all zeros, an attacker would *still* have to accurately model every single other entropy source also in use. - The RNG now reseeds itself quite rapidly during boot, starting at 2 seconds, then 4, then 8, then 16, and so forth, so that other sources of entropy get used without much delay. - Paranoid users can set random.trust_{cpu,bootloader}=no in the kernel command line, and paranoid system builders can set the Kconfig options to N, so there's no reduction or restriction of optionality. - It's a practical default. - All the distros have it set this way. Microsoft and Apple trust it too. Bandwagon. Cons: - RDRAND *could* still be backdoored with something like a fixed key or limited space serial number seed or another indexable scheme like that. (However, it's hard to imagine threat models where the CPU is backdoored like this, yet people are still okay making *any* computations with it or connecting it to networks, etc.) - RDRAND *could* be defective, rather than backdoored, and produce garbage that is in one way or another insufficient for crypto. - Suggesting a *reduction* in paranoia, as this commit effectively does, may cause some to question my personal integrity as a "security person". - Bootloader seeds and RDRAND are generally very difficult if not all together impossible to audit. Keep in mind that this doesn't actually change any behavior. This is just a change in the default Kconfig value. The distros already are shipping kernels that set things this way. Ard made an additional argument in [1]: We're at the mercy of firmware and micro-architecture anyway, given that we are also relying on it to ensure that every instruction in the kernel's executable image has been faithfully copied to memory, and that the CPU implements those instructions as documented. So I don't think firmware or ISA bugs related to RNGs deserve special treatment - if they are broken, we should quirk around them like we usually do. So enabling these by default is a step in the right direction IMHO. In [2], Phil pointed out that having this disabled masked a bug that CI otherwise would have caught: A clean 5.15.45 boots cleanly, whereas a downstream kernel shows the static key warning (but it does go on to boot). The significant difference is that our defconfigs set CONFIG_RANDOM_TRUST_BOOTLOADER=y defining that on top of multi_v7_defconfig demonstrates the issue on a clean 5.15.45. Conversely, not setting that option in a downstream kernel build avoids the warning [1] https://lore.kernel.org/lkml/CAMj1kXGi+ieviFjXv9zQBSaGyyzeGW_VpMpTLJK8PJb2QHEQ-w@mail.gmail.com/ [2] https://lore.kernel.org/lkml/c47c42e3-1d56-5859-a6ad-976a1a3381c6@raspberrypi.com/ Cc: Theodore Ts'o Reviewed-by: Ard Biesheuvel Signed-off-by: Jason A. Donenfeld Signed-off-by: Sasha Levin

random: account for arch randomness in bits

2022-06-14T16:45:20Z

commit 77fc95f8c0dc9e1f8e620ec14d2fb65028fb7adc upstream. Rather than accounting in bytes and multiplying (shifting), we can just account in bits and avoid the shift. The main motivation for this is there are other patches in flux that expand this code a bit, and avoiding the duplication of "* 8" everywhere makes things a bit clearer. Cc: stable@vger.kernel.org Fixes: 12e45a2a6308 ("random: credit architectural init the exact amount") Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman

random: mark bootloader randomness code as __init

2022-06-14T16:45:20Z

commit 39e0f991a62ed5efabd20711a7b6e7da92603170 upstream. add_bootloader_randomness() and the variables it touches are only used during __init and not after, so mark these as __init. At the same time, unexport this, since it's only called by other __init code that's built-in. Cc: stable@vger.kernel.org Fixes: 428826f5358c ("fdt: add support for rng-seed") Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman

random: avoid checking crng_ready() twice in random_init()

2022-06-14T16:45:20Z

commit 9b29b6b20376ab64e1b043df6301d8a92378e631 upstream. The current flow expands to: if (crng_ready()) ... else if (...) if (!crng_ready()) ... The second crng_ready() call is redundant, but can't so easily be optimized out by the compiler. This commit simplifies that to: if (crng_ready() ... else if (...) ... Fixes: 560181c27b58 ("random: move initialization functions out of hot pages") Cc: stable@vger.kernel.org Cc: Dominik Brodowski Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman

virtio-rng: make device ready before making request

2022-06-14T16:45:20Z

commit 228432551bd8783211e494ab35f42a4344580502 upstream. Current virtio-rng does a entropy request before DRIVER_OK, this violates the spec: virtio spec requires that all drivers set DRIVER_OK before using devices. Further, kernel will ignore the interrupt after commit 8b4ec69d7e09 ("virtio: harden vring IRQ"). Fixing this by making device ready before the request. Cc: stable@vger.kernel.org Fixes: 8b4ec69d7e09 ("virtio: harden vring IRQ") Fixes: f7f510ec1957 ("virtio: An entropy device, as suggested by hpa.") Reported-and-tested-by: syzbot+5b59d6d459306a556f54@syzkaller.appspotmail.com Signed-off-by: Jason Wang Message-Id: <20220608061422.38437-1-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin Reviewed-by: Laurent Vivier Signed-off-by: Greg Kroah-Hartman

char: xillybus: fix a refcount leak in cleanup_dev()

2022-06-14T16:45:10Z

[ Upstream commit b67d19662fdee275c479d21853bc1239600a798f ] usb_get_dev is called in xillyusb_probe. So it is better to call usb_put_dev before xdev is released. Acked-by: Eli Billauer Signed-off-by: Hangyu Hua Link: https://lore.kernel.org/r/20220406075703.23464-1-hbh25y@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

Revert "random: use static branch for crng_ready()"

2022-06-09T08:30:55Z

This reverts upstream commit f5bda35fba615ace70a656d4700423fa6c9bebee from stable. It's not essential and will take some time during 5.19 to work out properly. Signed-off-by: Jason A. Donenfeld

ipmi:ipmb: Fix refcount leak in ipmi_ipmb_probe

2022-06-09T08:30:41Z

commit a508e33956b538e034ed5df619a73ec7c15bda72 upstream. of_parse_phandle() returns a node pointer with refcount incremented, we should use of_node_put() on it when done. Add missing of_node_put() to avoid refcount leak. Fixes: 00d93611f002 ("ipmi:ipmb: Add the ability to have a separate slave and master device") Signed-off-by: Miaoqian Lin Message-Id: <20220512044445.3102-1-linmq006@gmail.com> Cc: stable@vger.kernel.org # v5.17+ Signed-off-by: Corey Minyard Signed-off-by: Greg Kroah-Hartman

hwrng: omap3-rom - fix using wrong clk_disable() in omap_rom_rng_runtime_resume()

2022-06-09T08:30:31Z

[ Upstream commit e4e62bbc6aba49a5edb3156ec65f6698ff37d228 ] 'ddata->clk' is enabled by clk_prepare_enable(), it should be disabled by clk_disable_unprepare(). Fixes: 8d9d4bdc495f ("hwrng: omap3-rom - Use runtime PM instead of custom functions") Signed-off-by: Yang Yingliang Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin

hwrng: cn10k - Make check_rng_health() return an error code

2022-06-09T08:30:25Z

[ Upstream commit 32547a6aedda132907fcd15cdc8271429609f216 ] Currently check_rng_health() returns zero unconditionally. Make it to output an error code and return it. Fixes: 38e9791a0209 ("hwrng: cn10k - Add random number generator support") Signed-off-by: Vladis Dronov Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin