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authorJohn David Anglin <dave.anglin@bell.net>2017-11-12 01:11:16 +0300
committerHelge Deller <deller@gmx.de>2017-11-17 17:27:13 +0300
commit05f016d2ca7a4fab99d5d5472168506ddf95e74f (patch)
treed020d10f9e2c17fee084cd5471c36f957ded604c /arch
parentbebc6082da0a9f5d47a1ea2edc099bf671058bd4 (diff)
downloadlinux-05f016d2ca7a4fab99d5d5472168506ddf95e74f.tar.xz
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/parisc/kernel/syscall.S6
1 files 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