This is a note to let you know that I've just added the patch titled
parisc: Fix validity check of pointer size argument in new CAS implementation
to the 4.4-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-fix-validity-check-of-pointer-size-argument-in-new-cas-implementation.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 05f016d2ca7a4fab99d5d5472168506ddf95e74f Mon Sep 17 00:00:00 2001
From: John David Anglin <dave.anglin@xxxxxxxx>
Date: Sat, 11 Nov 2017 17:11:16 -0500
Subject: parisc: Fix validity check of pointer size argument in new CAS implementation
From: John David Anglin <dave.anglin@xxxxxxxx>
commit 05f016d2ca7a4fab99d5d5472168506ddf95e74f upstream.
As noted by Christoph Biedl, passing a pointer size of 4 in the new CAS
implementation causes a kernel crash. The attached patch corrects the
off by one error in the argument validity check.
In reviewing the code, I noticed that we only perform word operations
with the pointer size argument. The subi instruction intentionally uses
a word condition on 64-bit kernels. Nullification was used instead of a
cmpib instruction as the branch should never be taken. The shlw
pseudo-operation generates a depw,z instruction and it clears the target
before doing a shift left word deposit. Thus, we don't need to clip the
upper 32 bits of this argument on 64-bit kernels.
Tested with a gcc testsuite run with a 64-bit kernel. The gcc atomic
code in libgcc is the only direct user of the new CAS implementation
that I am aware of.
Signed-off-by: John David Anglin <dave.anglin@xxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/kernel/syscall.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -688,15 +688,15 @@ cas_action:
/* ELF32 Process entry path */
lws_compare_and_swap_2:
#ifdef CONFIG_64BIT
- /* Clip the input registers */
+ /* Clip the input registers. We don't need to clip %r23 as we
+ only use it for word operations */
depdi 0, 31, 32, %r26
depdi 0, 31, 32, %r25
depdi 0, 31, 32, %r24
- depdi 0, 31, 32, %r23
#endif
/* Check the validity of the size pointer */
- subi,>>= 4, %r23, %r0
+ subi,>>= 3, %r23, %r0
b,n lws_exit_nosys
/* Jump to the functions which will load the old and new values into
Patches currently in stable-queue which might be from dave.anglin@xxxxxxxx are
queue-4.4/parisc-fix-validity-check-of-pointer-size-argument-in-new-cas-implementation.patch