From: Ard Biesheuvel <ardb@kernel.org>
To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>
Cc: Ard Biesheuvel <ardb@kernel.org>,
linux-kernel@vger.kernel.org,
Arvind Sankar <nivedita@alum.mit.edu>,
Atish Patra <atish.patra@wdc.com>,
Palmer Dabbelt <palmerdabbelt@google.com>,
Zou Wei <zou_wei@huawei.com>
Subject: [PATCH 20/33] efi/libstub/random: Increase random alloc granularity
Date: Fri, 24 Apr 2020 15:05:18 +0200 [thread overview]
Message-ID: <20200424130531.30518-21-ardb@kernel.org> (raw)
In-Reply-To: <20200424130531.30518-1-ardb@kernel.org>
The implementation of efi_random_alloc() arbitrarily truncates the
provided random seed to 16 bits, which limits the granularity of the
randomly chosen allocation offset in memory. This is currently only
an issue if the size of physical memory exceeds 128 GB, but going
forward, we will reduce the allocation alignment to 64 KB, and this
means we need to increase the granularity to ensure that the random
memory allocations are distributed evenly.
We will need to switch to 64-bit arithmetic for the multiplication,
but this does not result in 64-bit integer intrinsic calls on ARM or
on i386.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/efi/libstub/randomalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
index 6200dfa650f5..a408df474d83 100644
--- a/drivers/firmware/efi/libstub/randomalloc.c
+++ b/drivers/firmware/efi/libstub/randomalloc.c
@@ -87,7 +87,7 @@ efi_status_t efi_random_alloc(unsigned long size,
}
/* find a random number between 0 and total_slots */
- target_slot = (total_slots * (u16)random_seed) >> 16;
+ target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
/*
* target_slot is now a value in the range [0, total_slots), and so
--
2.17.1
next prev parent reply other threads:[~2020-04-24 13:07 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-24 13:04 [GIT PULL 00/33] EFI updates for v5.8 Ard Biesheuvel
2020-04-24 13:04 ` [PATCH 01/33] efi/libstub: Move arm-stub to a common file Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 02/33] efi/libstub: Make initrd file loader configurable Ard Biesheuvel
2020-04-24 13:15 ` Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 03/33] efi/libstub: Unify EFI call wrappers for non-x86 Ard Biesheuvel
2020-05-03 15:09 ` Guenter Roeck
2020-05-03 16:09 ` Arvind Sankar
2020-05-03 16:11 ` Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 04/33] efi/libstub/arm: Make install_memreserve_table static Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 05/33] efi/gop: Remove redundant current_fb_base Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 06/33] efi/gop: Move check for framebuffer before con_out Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 07/33] efi/gop: Get mode information outside the loop Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 08/33] efi/gop: Factor out locating the gop into a function Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 09/33] efi/gop: Slightly re-arrange logic of find_gop Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 10/33] efi/gop: Move variable declarations into loop block Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 11/33] efi/gop: Use helper macros for populating lfb_base Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 12/33] efi/gop: Use helper macros for find_bits Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 13/33] efi/gop: Remove unreachable code from setup_pixel_info Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 14/33] efi/gop: Add prototypes for query_mode and set_mode Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 15/33] efi/gop: Allow specifying mode number on command line Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 16/33] efi/gop: Allow specifying mode by <xres>x<yres> Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 17/33] efi/gop: Allow specifying depth as well as resolution Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 18/33] efi/gop: Allow automatically choosing the best mode Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 19/33] efi/libstub/random: Align allocate size to EFI_ALLOC_ALIGN Ard Biesheuvel
2020-04-24 13:05 ` Ard Biesheuvel [this message]
2020-04-24 13:05 ` [PATCH 21/33] efi/libstub/arm64: Replace 'preferred' offset with alignment check Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 22/33] efi/libstub/arm64: Simplify randomized loading of kernel image Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 23/33] efi/libstub: Add API function to allocate aligned memory Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 24/33] efi/libstub/arm64: Switch to ordinary page allocator for kernel image Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 25/33] efi/libstub: Move efi_relocate_kernel() into separate source file Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 26/33] efi/arm: Remove __efistub_global annotation Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 27/33] efi/x86: Remove __efistub_global and add relocation check Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 28/33] efi: Kill __efistub_global Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 29/33] efi/libstub: Drop __pure getter for efi_system_table Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 30/33] efi/libstub: Drop __pure getters for EFI stub options Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 31/33] efi/libstub/x86: Avoid getter function for efi_is64 Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 32/33] efi: Clean up config table description arrays Ard Biesheuvel
2020-04-24 13:05 ` [PATCH 33/33] efi: Move arch_tables check to caller Ard Biesheuvel
2020-04-25 8:27 ` [GIT PULL 00/33] EFI updates for v5.8 Ingo Molnar
2020-04-25 9:57 ` Ard Biesheuvel
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