From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-efi@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Brown <broonie@kernel.org>
Subject: [PATCH v3 19/30] arm64: kaslr: deal with init called with VA randomization enabled
Date: Mon, 11 Apr 2022 11:48:13 +0200 [thread overview]
Message-ID: <20220411094824.4176877-20-ardb@kernel.org> (raw)
In-Reply-To: <20220411094824.4176877-1-ardb@kernel.org>
We will be entering kaslr_init() fully randomized, and so any addresses
taken by this code already take the randomization into account.
This means that taking the address of _end or _etext and adding offset
to it produces the wrong value, given that _end and _etext references
will have been fixed up already, and therefore already incorporate
offset.
So instead of referring to these symbols directly, use their offsets
relative to _text, which should produce values that depend on the size
and layout of the Image only. Then, add KIMAGE_VADDR to obtain the
unrandomized values.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/kaslr.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index d5542666182f..3b12715642ce 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -141,6 +141,8 @@ u64 __init kaslr_early_init(void)
return offset % SZ_2G;
if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
+ u64 end = (u64)_end - (u64)_text + KIMAGE_VADDR;
+
/*
* Randomize the module region over a 2 GB window covering the
* kernel. This reduces the risk of modules leaking information
@@ -150,9 +152,11 @@ u64 __init kaslr_early_init(void)
* resolved normally.)
*/
module_range = SZ_2G - (u64)(_end - _stext);
- module_alloc_base = max((u64)_end + offset - SZ_2G,
+ module_alloc_base = max(end + offset - SZ_2G,
(u64)MODULES_VADDR);
} else {
+ u64 end = (u64)_etext - (u64)_text + KIMAGE_VADDR;
+
/*
* Randomize the module region by setting module_alloc_base to
* a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,
@@ -163,7 +167,7 @@ u64 __init kaslr_early_init(void)
* when ARM64_MODULE_PLTS is enabled.
*/
module_range = MODULES_VSIZE - (u64)(_etext - _stext);
- module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;
+ module_alloc_base = end + offset - MODULES_VSIZE;
}
/* use the lower 21 bits to randomize the base of the module region */
--
2.30.2
next prev parent reply other threads:[~2022-04-11 9:50 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-11 9:47 [PATCH v3 00/30] arm64: support WXN and entry with MMU enabled Ard Biesheuvel
2022-04-11 9:47 ` [PATCH v3 01/30] arm64: head: move kimage_vaddr variable into C file Ard Biesheuvel
2022-04-11 9:47 ` [PATCH v3 02/30] arm64: mm: make vabits_actual a build time constant if possible Ard Biesheuvel
2022-04-11 9:47 ` [PATCH v3 03/30] arm64: head: move assignment of idmap_t0sz to C code Ard Biesheuvel
2022-04-11 9:47 ` [PATCH v3 04/30] arm64: head: drop idmap_ptrs_per_pgd Ard Biesheuvel
2022-04-11 9:47 ` [PATCH v3 05/30] arm64: head: simplify page table mapping macros (slightly) Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 06/30] arm64: head: switch to map_memory macro for the extended ID map Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 07/30] arm64: head: split off idmap creation code Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 08/30] arm64: kernel: drop unnecessary PoC cache clean+invalidate Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 09/30] arm64: head: pass ID map root table address to __enable_mmu() Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 10/30] arm64: mm: provide idmap pointer to cpu_replace_ttbr1() Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 11/30] arm64: head: add helper function to remap regions in early page tables Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 12/30] arm64: head: cover entire kernel image in initial ID map Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 13/30] arm64: head: use relative references to the RELA and RELR tables Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 14/30] arm64: head: create a temporary FDT mapping in the initial ID map Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 15/30] arm64: idreg-override: use early FDT mapping in " Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 16/30] arm64: head: factor out TTBR1 assignment into a macro Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 17/30] arm64: head: populate kernel page tables with MMU and caches on Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 18/30] arm64: head: record CPU boot mode after enabling the MMU Ard Biesheuvel
2022-04-11 9:48 ` Ard Biesheuvel [this message]
2022-04-11 9:48 ` [PATCH v3 20/30] arm64: head: relocate kernel only a single time if KASLR is enabled Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 21/30] arm64: head: remap the kernel text/inittext region read-only Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 22/30] arm64: setup: drop early FDT pointer helpers Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 23/30] arm64: mm: move ro_after_init section into the data segment Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 24/30] arm64: mm: add support for WXN memory translation attribute Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 25/30] arm64: head: record the MMU state at primary entry Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 26/30] arm64: head: avoid cache invalidation when entering with the MMU on Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 27/30] arm64: head: clean the ID map page to the PoC Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 28/30] efi: libstub: pass image handle to handle_kernel_image() Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 29/30] efi/arm64: libstub: run image in place if randomized by the loader Ard Biesheuvel
2022-04-11 9:48 ` [PATCH v3 30/30] arm64: efi/libstub: enter with the MMU on if executing in place Ard Biesheuvel
2022-04-12 16:59 ` [PATCH v3 00/30] arm64: support WXN and entry with MMU enabled Kees Cook
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