[4.19.y-cip] m68k: Update ->thread.esp0 before calling syscall_trace() in ret_from_signal

Commit Message

Finn Thain Feb. 13, 2025, 7:24 a.m. UTC

From: Al Viro <[e-mail]>

[ 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 <[e-mail]>
Fixes: bd6f56a75bb2 ("m68k: Missing syscall_trace() on sigreturn")
Signed-off-by: Al Viro <[e-mail]>
Tested-by: Michael Schmitz <[e-mail]>
Reviewed-by: Michael Schmitz <[e-mail]>
Tested-by: Finn Thain <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Finn Thain <[e-mail]>
---
 arch/m68k/kernel/entry.S | 2 ++
 1 file changed, 2 insertions(+)

Patch

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