linux-kernel - [PATCH 5.10.y] m68k: Update ->thread.esp0 before calling syscall_trace() in ret_from

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Message-ID: <b2d405a9b410211f27e87f8a0de4b10a@linux-m68k.org>
Date: Mon, 18 Nov 2024 16:27:18 +1100
From: Finn Thain <fthain@...ux-m68k.org>
To: stable@...nel.org
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>, Al Viro <viro@...iv.linux.org.uk>, linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5.10.y] m68k: Update ->thread.esp0 before calling syscall_trace() in ret_from_signal

From: Al Viro <viro@...iv.linux.org.uk>

[ Upstream commit 50e43a57334400668952f8e551c9d87d3ed2dfef ]

We get there when sigreturn has performed obscene acts on kernel stack;
in particular, the location of pt_regs has shifted.  We are about to call
syscall_trace(), which might stop for tracer.  If that happens, we'd better
have task_pt_regs() returning correct result...

Fucked-up-by: Al Viro <viro@...iv.linux.org.uk>
Fixes: bd6f56a75bb2 ("m68k: Missing syscall_trace() on sigreturn")
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Tested-by: Michael Schmitz <schmitzmic@...il.com>
Reviewed-by: Michael Schmitz <schmitzmic@...il.com>
Tested-by: Finn Thain <fthain@...ux-m68k.org>
Link: https://lore.kernel.org/r/YP2dMWeV1LkHiOpr@zeniv-ca.linux.org.uk
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Signed-off-by: Finn Thain <fthain@...ux-m68k.org>
---
 arch/m68k/kernel/entry.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index 417d8f0e8962..0d03b4f2077b 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -182,6 +182,8 @@ ENTRY(ret_from_signal)
 	movel	%curptr@(TASK_STACK),%a1
 	tstb	%a1@(TINFO_FLAGS+2)
 	jge	1f
+	lea	%sp@(SWITCH_STACK_SIZE),%a1
+	movel	%a1,%curptr@(TASK_THREAD+THREAD_ESP0)
 	jbsr	syscall_trace
 1:	RESTORE_SWITCH_STACK
 	addql	#4,%sp