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From a79ebe4eb65331733803df4a7fd634d3b709af7b Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Tue, 24 Feb 2015 16:30:21 +0000
Subject: [PATCH] arm64: Fix text patching logic when using fixmap
Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
the way we patch the kernel text, using a fixmap when the kernel or
modules are flagged as read only.
Unfortunately, a flaw in the logic makes it fall over when patching
modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
[...]
[ 32.032636] Call trace:
[ 32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
[ 32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
[ 32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
[ 32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
[ 32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
[ 32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
[ 32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
[ 32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
[ 32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
[...]
This is triggered by the use of virt_to_page() on a module address,
which ends to pointing to Nowhereland if you're lucky, or corrupt
your precious data if not.
This patch fixes the logic by mimicking what is done on arm:
- If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
use vmalloc_to_page().
- If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
use virt_to_page().
- Otherwise, use the provided address, as we can write to it directly.
Tested on 4.0-rc1 as a KVM guest.
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/kernel/insn.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 27d4864..c8eca88 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
page = vmalloc_to_page(addr);
- else
+ else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
page = virt_to_page(addr);
+ else
+ return addr;
BUG_ON(!page);
set_fixmap(fixmap, page_to_phys(page));
--
2.3.0
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