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commitf7e67b8e80upstream. Currently, if CONFIG_RANDOM_TRUST_BOOTLOADER is enabled, multiple calls to add_bootloader_randomness() are broken and can cause a NULL pointer dereference, as noted by Ivan T. Ivanov. This is not only a hypothetical problem, as qemu on arm64 may provide bootloader entropy via EFI and via devicetree. On the first call to add_hwgenerator_randomness(), crng_fast_load() is executed, and if the seed is long enough, crng_init will be set to 1. On subsequent calls to add_bootloader_randomness() and then to add_hwgenerator_randomness(), crng_fast_load() will be skipped. Instead, wait_event_interruptible() and then credit_entropy_bits() will be called. If the entropy count for that second seed is large enough, that proceeds to crng_reseed(). However, both wait_event_interruptible() and crng_reseed() depends (at least in numa_crng_init()) on workqueues. Therefore, test whether system_wq is already initialized, which is a sufficient indicator that workqueue_init_early() has progressed far enough. If we wind up hitting the !system_wq case, we later want to do what would have been done there when wqs are up, so set a flag, and do that work later from the rand_initialize() call. Reported-by: Ivan T. Ivanov <iivanov@suse.de> Fixes:18b915ac6b("efi/random: Treat EFI_RNG_PROTOCOL output as bootloader randomness") Cc: stable@vger.kernel.org Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> [Jason: added crng_need_done state and related logic.] Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.