The patch below does not apply to the 4.19-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