powerpc/vdso64: Use double word compare on pointers

__kernel_get_syscall_map() and __kernel_clock_getres() use cmpli to
check if the passed in pointer is non zero. cmpli maps to a 32 bit
compare on binutils, so we ignore the top 32 bits.

A simple test case can be created by passing in a bogus pointer with
the bottom 32 bits clear. Using a clk_id that is handled by the VDSO,
then one that is handled by the kernel shows the problem:

  printf("%d\n", clock_getres(CLOCK_REALTIME, (void *)0x100000000));
  printf("%d\n", clock_getres(CLOCK_BOOTTIME, (void *)0x100000000));

And we get:

  0
  -1

The bigger issue is if we pass a valid pointer with the bottom 32 bits
clear, in this case we will return success but won't write any data
to the pointer.

I stumbled across this issue because the LLVM integrated assembler
doesn't accept cmpli with 3 arguments. Fix this by converting them to
cmpldi.

Fixes: a7f290dad3 ("[PATCH] powerpc: Merge vdso's and add vdso support to 32 bits kernel")
Cc: stable@vger.kernel.org # v2.6.15+
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Anton Blanchard 2016-09-25 17:16:53 +10:00 committed by Michael Ellerman
parent 2e5bbb5461
commit 5045ea3737
2 changed files with 2 additions and 2 deletions

View File

@ -59,7 +59,7 @@ V_FUNCTION_BEGIN(__kernel_get_syscall_map)
bl V_LOCAL_FUNC(__get_datapage)
mtlr r12
addi r3,r3,CFG_SYSCALL_MAP64
cmpli cr0,r4,0
cmpldi cr0,r4,0
crclr cr0*4+so
beqlr
li r0,NR_syscalls

View File

@ -145,7 +145,7 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
bne cr0,99f
li r3,0
cmpli cr0,r4,0
cmpldi cr0,r4,0
crclr cr0*4+so
beqlr
lis r5,CLOCK_REALTIME_RES@h