From: John David Anglin Date: Sat, 11 Nov 2017 22:11:16 +0000 (-0500) Subject: parisc: Fix validity check of pointer size argument in new CAS implementation X-Git-Tag: v3.18.85~27 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c7ac1d7390e934e1aec27170a512edfaac25809b;p=thirdparty%2Fkernel%2Fstable.git parisc: Fix validity check of pointer size argument in new CAS implementation 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 Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 95f090fe385a0..196395a0ac917 100644 --- 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