FAILED: patch "[PATCH] parisc/entry: fix trace test in syscall exit path" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3ec18fc7831e7d79e2d536dd1f3bc0d3ba425e8a Mon Sep 17 00:00:00 2001
From: Sven Schnelle <[email protected]>
Date: Sat, 13 Nov 2021 20:41:17 +0100
Subject: [PATCH] parisc/entry: fix trace test in syscall exit path

commit 8779e05ba8aa ("parisc: Fix ptrace check on syscall return") fixed testing of TI_FLAGS. This uncovered a bug in the test mask. syscall_restore_rfi is only used when the kernel needs to exit to usespace with single or block stepping and the recovery counter enabled. The test however used _TIF_SYSCALL_TRACE_MASK, which includes a lot of bits that shouldn't be tested here.

Fix this by using TIF_SINGLESTEP and TIF_BLOCKSTEP directly.

I encountered this bug by enabling syscall tracepoints. Both in qemu and on real hardware. As soon as i enabled the tracepoint (sys_exit_read, but i guess it doesn't really matter which one), i got random page faults in userspace almost immediately.

index 57944d6f9ebb..88c188a965d8 100644
@@ -1805,7 +1805,7 @@ syscall_restore:
 
 	/* Are we being ptraced? */
 	LDREG	TASK_TI_FLAGS(%r1),%r19
-	ldi	_TIF_SYSCALL_TRACE_MASK,%r2
+	ldi	_TIF_SINGLESTEP|_TIF_BLOCKSTEP,%r2
 	and,COND(=)	%r19,%r2,%r0
 	b,n	syscall_restore_rfi