From 05f016d2ca7a4fab99d5d5472168506ddf95e74f Mon Sep 17 00:00:00 2001 From: John David Anglin <dave.anglin@bell.net> Date: Sat, 11 Nov 2017 17:11:16 -0500 Subject: [PATCH] parisc: Fix validity check of pointer size argument in new CAS implementation 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@bell.net> Cc: stable@vger.kernel.org # 3.13+ Signed-off-by: Helge Deller <deller@gmx.de> --- arch/parisc/kernel/syscall.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 41e60a9c7db2..e775f80ae28c 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -690,15 +690,15 @@ 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 -- GitLab