linux-kernel - [PATCH 5.10 23/43] arm64: entry.S: Add ventry overflow sanity checks

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Date:   Wed,  9 Mar 2022 16:59:56 +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,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>
Subject: [PATCH 5.10 23/43] arm64: entry.S: Add ventry overflow sanity checks

From: James Morse <james.morse@....com>

commit 4330e2c5c04c27bebf89d34e0bc14e6943413067 upstream.

Subsequent patches add even more code to the ventry slots.
Ensure kernels that overflow a ventry slot don't get built.

Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: James Morse <james.morse@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/kernel/entry.S |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -62,6 +62,7 @@
 
 	.macro kernel_ventry, el, label, regsize = 64
 	.align 7
+.Lventry_start\@:
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 	.if	\el == 0
 alternative_if ARM64_UNMAP_KERNEL_AT_EL0
@@ -120,6 +121,7 @@ alternative_else_nop_endif
 	mrs	x0, tpidrro_el0
 #endif
 	b	el\()\el\()_\label
+.org .Lventry_start\@ + 128	// Did we overflow the ventry slot?
 	.endm
 
 	.macro tramp_alias, dst, sym
@@ -832,6 +834,7 @@ alternative_else_nop_endif
 	add	x30, x30, #(1b - tramp_vectors)
 	isb
 	ret
+.org 1b + 128	// Did we overflow the ventry slot?
 	.endm
 
 	.macro tramp_exit, regsize = 64