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 <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 3ec18fc7831e7d79e2d536dd1f3bc0d3ba425e8a Mon Sep 17 00:00:00 2001
From: Sven Schnelle <svens@xxxxxxxxxxxxxx>
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.
Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 57944d6f9ebb..88c188a965d8 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -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
