Patch "Revert "arm64: Stash shadow stack pointer in the task struct on interrupt"" has been added to the 5.10-stable tree

[gregkh at linuxfoundation.org]

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

    Revert "arm64: Stash shadow stack pointer in the task struct on interrupt"

to the 5.10-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:
     revert-arm64-stash-shadow-stack-pointer-in-the-task-struct-on-interrupt.patch
and it can be found in the queue-5.10 subdirectory.

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


>From xiangyang3 at huawei.com  Tue Feb 20 16:30:54 2024
From: Xiang Yang <xiangyang3 at huawei.com>
Date: Mon, 19 Feb 2024 21:21:53 +0800
Subject: Revert "arm64: Stash shadow stack pointer in the task struct on interrupt"
To: <ardb at kernel.org>, <mark.rutland at arm.com>, <catalin.marinas at arm.com>, <will at kernel.org>
Cc: <keescook at chromium.org>, <linux-arm-kernel at lists.infradead.org>, <stable at vger.kernel.org>, <gregkh at linuxfoundation.org>, <xiangyang3 at huawei.com>, <xiujianfeng at huawei.com>, <liaochang1 at huawei.com>
Message-ID: <20240219132153.378265-1-xiangyang3 at huawei.com>


This reverts commit 3f225f29c69c13ce1cbdb1d607a42efeef080056 which is
commit 59b37fe52f49955791a460752c37145f1afdcad1 upstream.

The shadow call stack for irq now is stored in current task's thread info
in irq_stack_entry. There is a possibility that we have some soft irqs
pending at the end of hard irq, and when we process softirq with the irq
enabled, irq_stack_entry will enter again and overwrite the shadow call
stack whitch stored in current task's thread info, leading to the
incorrect shadow call stack restoration for the first entry of the hard
IRQ, then the system end up with a panic.

task A                               |  task A
-------------------------------------+------------------------------------
el1_irq        //irq1 enter          |
  irq_handler  //save scs_sp1        |
    gic_handle_irq                   |
    irq_exit                         |
      __do_softirq                   |
                                     | el1_irq         //irq2 enter
                                     |   irq_handler   //save scs_sp2
                                     |                 //overwrite scs_sp1
                                     |   ...
                                     |   irq_stack_exit //restore scs_sp2
  irq_stack_exit //restore wrong     |
                 //scs_sp2           |

So revert this commit to fix it.

Fixes: 3f225f29c69c ("arm64: Stash shadow stack pointer in the task struct on interrupt")
Signed-off-by: Xiang Yang <xiangyang3 at huawei.com>
Acked-by: Ard Biesheuvel <ardb at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 arch/arm64/kernel/entry.S |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -431,7 +431,9 @@ SYM_CODE_END(__swpan_exit_el0)
 
 	.macro	irq_stack_entry
 	mov	x19, sp			// preserve the original sp
-	scs_save tsk			// preserve the original shadow stack
+#ifdef CONFIG_SHADOW_CALL_STACK
+	mov	x24, scs_sp		// preserve the original shadow stack
+#endif
 
 	/*
 	 * Compare sp with the base of the task stack.
@@ -465,7 +467,9 @@ SYM_CODE_END(__swpan_exit_el0)
 	 */
 	.macro	irq_stack_exit
 	mov	sp, x19
-	scs_load_current
+#ifdef CONFIG_SHADOW_CALL_STACK
+	mov	scs_sp, x24
+#endif
 	.endm
 
 /* GPRs used by entry code */


Patches currently in stable-queue which might be from xiangyang3 at huawei.com are

queue-5.10/revert-arm64-stash-shadow-stack-pointer-in-the-task-struct-on-interrupt.patch