Patch "arm64: entry: Restore tramp_map_kernel ISB" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    arm64: entry: Restore tramp_map_kernel ISB

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-entry-restore-tramp_map_kernel-isb.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From james.morse@arm.com  Thu Jul 14 20:32:47 2022
From: James Morse <james.morse@arm.com>
Date: Thu, 14 Jul 2022 17:22:25 +0100
Subject: arm64: entry: Restore tramp_map_kernel ISB
To: stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>, James Morse <james.morse@arm.com>, Sumit Gupta <sumitg@nvidia.com>
Message-ID: <20220714162225.280073-1-james.morse@arm.com>

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

Summit reports that the BHB backports for v4.9 prevent vulnerable
platforms from booting when CONFIG_RANDOMIZE_BASE is enabled.

This is because the trampoline code takes a translation fault when
accessing the data page, because the TTBR write hasn't been completed
by an ISB before the access is made.

Upstream has a complex erratum workaround for QCOM_FALKOR_E1003 in
this area, which removes the ISB when the workaround has been applied.
v4.9 lacks this workaround, but should still have the ISB.

Restore the barrier.

Fixes: aee10c2dd013 ("arm64: entry: Add macro for reading symbol addresses from the trampoline")
Reported-by: Sumit Gupta <sumitg@nvidia.com>
Tested-by: Sumit Gupta <sumitg@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm64/kernel/entry.S |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -964,6 +964,7 @@ __ni_sys_trace:
 	b	.
 2:
 	tramp_map_kernel	x30
+	isb
 	tramp_data_read_var	x30, vectors
 	prfm	plil1strm, [x30, #(1b - \vector_start)]
 	msr	vbar_el1, x30


Patches currently in stable-queue which might be from james.morse@arm.com are

queue-4.9/arm64-entry-restore-tramp_map_kernel-isb.patch

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