This is a note to let you know that I've just added the patch titled
parisc/entry: fix trace test in syscall exit path
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-entry-fix-trace-test-in-syscall-exit-path.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3ec18fc7831e7d79e2d536dd1f3bc0d3ba425e8a Mon Sep 17 00:00:00 2001
From: Sven Schnelle <svens@xxxxxxxxxxxxxx>
Date: Sat, 13 Nov 2021 20:41:17 +0100
Subject: parisc/entry: fix trace test in syscall exit path
From: Sven Schnelle <svens@xxxxxxxxxxxxxx>
commit 3ec18fc7831e7d79e2d536dd1f3bc0d3ba425e8a upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/kernel/entry.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -1850,7 +1850,7 @@ syscall_restore:
/* Are we being ptraced? */
LDREG TI_FLAGS-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r19
- ldi _TIF_SYSCALL_TRACE_MASK,%r2
+ ldi _TIF_SINGLESTEP|_TIF_BLOCKSTEP,%r2
and,COND(=) %r19,%r2,%r0
b,n syscall_restore_rfi
Patches currently in stable-queue which might be from svens@xxxxxxxxxxxxxx are
queue-4.9/parisc-kgdb-add-kgdb_roundup-to-make-kgdb-work-with-.patch
queue-4.9/parisc-fix-warning-in-flush_tlb_all.patch
queue-4.9/parisc-entry-fix-trace-test-in-syscall-exit-path.patch
