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Date: Tue, 10 Mar 2020 13:40:25 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>, Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>, linux-efi@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de> Subject: [PATCH 5.5 188/189] efi: READ_ONCE rng seed size before munmap From: Jason A. Donenfeld <Jason@...c4.com> commit be36f9e7517e17810ec369626a128d7948942259 upstream. This function is consistent with using size instead of seed->size (except for one place that this patch fixes), but it reads seed->size without using READ_ONCE, which means the compiler might still do something unwanted. So, this commit simply adds the READ_ONCE wrapper. Fixes: 636259880a7e ("efi: Add support for seeding the RNG from a UEFI ...") Signed-off-by: Jason A. Donenfeld <Jason@...c4.com> Signed-off-by: Ard Biesheuvel <ardb@...nel.org> Signed-off-by: Ingo Molnar <mingo@...nel.org> Cc: linux-efi@...r.kernel.org Cc: Ingo Molnar <mingo@...nel.org> Cc: Thomas Gleixner <tglx@...utronix.de> Link: https://lore.kernel.org/r/20200217123354.21140-1-Jason@zx2c4.com Link: https://lore.kernel.org/r/20200221084849.26878-5-ardb@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/firmware/efi/efi.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -552,7 +552,7 @@ int __init efi_config_parse_tables(void seed = early_memremap(efi.rng_seed, sizeof(*seed)); if (seed != NULL) { - size = seed->size; + size = READ_ONCE(seed->size); early_memunmap(seed, sizeof(*seed)); } else { pr_err("Could not map UEFI random seed!\n"); @@ -562,7 +562,7 @@ int __init efi_config_parse_tables(void sizeof(*seed) + size); if (seed != NULL) { pr_notice("seeding entropy pool\n"); - add_bootloader_randomness(seed->bits, seed->size); + add_bootloader_randomness(seed->bits, size); early_memunmap(seed, sizeof(*seed) + size); } else { pr_err("Could not map UEFI random seed!\n");
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