Re: [PATCH] powerpc/pseries: Fix stack corruption in htpe code

[Benjamin Herrenschmidt <benh@au1.ibm.com>]

On Thu, 2016-10-06 at 20:32 +0530, Aneesh Kumar K.V wrote:
> Laurent Dufour <ldufour@linux.vnet.ibm.com> writes:
> 

(Off-list)

Did that bug make it to RHEL/CentOS/SLES ?

We also need to poke Ubuntu to get the fix ASAP.

> > This commit fixes a stack corruption in the pseries specific code
> > dealing
> > with the huge pages.
> > 
> > In __pSeries_lpar_hugepage_invalidate() the buffer used to pass
> > arguments
> > to the hypervisor is not large enough. This leads to a stack
> > corruption
> > where a previously saved register could be corrupted leading to
> > unexpected
> > result in the caller, like the following panic:
> > 
> > Oops: Kernel access of bad area, sig: 11 [#1]
> > SMP NR_CPUS=2048 NUMA pSeries
> > Modules linked in: virtio_balloon ip_tables x_tables autofs4
> > virtio_blk 8139too virtio_pci virtio_ring 8139cp virtio
> > CPU: 11 PID: 1916 Comm: mmstress Not tainted 4.8.0 #76
> > task: c000000005394880 task.stack: c000000005570000
> > NIP: c00000000027bf6c LR: c00000000027bf64 CTR: 0000000000000000
> > REGS: c000000005573820 TRAP: 0300   Not tainted  (4.8.0)
> > MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 84822884  XER:
> > 20000000
> > CFAR: c00000000010a924 DAR: 420000000014e5e0 DSISR: 40000000 SOFTE:
> > 1
> > GPR00: c00000000027bf64 c000000005573aa0 c000000000e02800
> > c000000004447964
> > GPR04: c00000000404de18 c000000004d38810 00000000042100f5
> > 00000000f5002104
> > GPR08: e0000000f5002104 0000000000000001 042100f5000000e0
> > 00000000042100f5
> > GPR12: 0000000000002200 c00000000fe02c00 c00000000404de18
> > 0000000000000000
> > GPR16: c1ffffffffffe7ff 00003fff62000000 420000000014e5e0
> > 00003fff63000000
> > GPR20: 0008000000000000 c0000000f7014800 0405e600000000e0
> > 0000000000010000
> > GPR24: c000000004d38810 c000000004447c10 c00000000404de18
> > c000000004447964
> > GPR28: c000000005573b10 c000000004d38810 00003fff62000000
> > 420000000014e5e0
> > NIP [c00000000027bf6c] zap_huge_pmd+0x4c/0x470
> > LR [c00000000027bf64] zap_huge_pmd+0x44/0x470
> > Call Trace:
> > [c000000005573aa0] [c00000000027bf64] zap_huge_pmd+0x44/0x470
> > (unreliable)
> > [c000000005573af0] [c00000000022bbd8] unmap_page_range+0xcf8/0xed0
> > [c000000005573c30] [c00000000022c2d4] unmap_vmas+0x84/0x120
> > [c000000005573c80] [c000000000235448] unmap_region+0xd8/0x1b0
> > [c000000005573d80] [c0000000002378f0] do_munmap+0x2d0/0x4c0
> > [c000000005573df0] [c000000000237be4] SyS_munmap+0x64/0xb0
> > [c000000005573e30] [c000000000009560] system_call+0x38/0x108
> > Instruction dump:
> > fbe1fff8 fb81ffe0 7c7f1b78 7ca32b78 7cbd2b78 f8010010 7c9a2378
> > f821ffb1
> > 7cde3378 4bfffea9 7c7b1b79 41820298 <e87f0000> 48000130 7fa5eb78
> > 7fc4f378
> > 
> > Most of the time, the bug is surfacing in a caller up in the stack
> > from
> > __pSeries_lpar_hugepage_invalidate() which is quite confusing.
> > 
> > This bug is pending since v3.11 but was hidden if a caller of the
> > caller of __pSeries_lpar_hugepage_invalidate() has pushed the
> > corruped
> > register (r18 in this case) in the stack and is not using it until
> > restoring it. GCC 6.2.0 seems to raise it more frequently.
> > 
> > This commit also change the definition of the parameter buffer in
> > pSeries_lpar_flush_hash_range() to rely on the global define
> > PLPAR_HCALL9_BUFSIZE (no functional change here).
> > 
> 
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> 
> > 
> > Fixes: 1a5272866f87 ("powerpc: Optimize hugepage invalidate")
> > Cc: <stable@vger.kernel.org>
> > Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> > Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
> > ---
> >  arch/powerpc/platforms/pseries/lpar.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/powerpc/platforms/pseries/lpar.c
> > b/arch/powerpc/platforms/pseries/lpar.c
> > index 86707e67843f..aa35245d8d6d 100644
> > --- a/arch/powerpc/platforms/pseries/lpar.c
> > +++ b/arch/powerpc/platforms/pseries/lpar.c
> > @@ -393,7 +393,7 @@ static void
> > __pSeries_lpar_hugepage_invalidate(unsigned long *slot,
> >  					     unsigned long *vpn,
> > int count,
> >  					     int psize, int ssize)
> >  {
> > -	unsigned long param[8];
> > +	unsigned long param[PLPAR_HCALL9_BUFSIZE];
> >  	int i = 0, pix = 0, rc;
> >  	unsigned long flags = 0;
> >  	int lock_tlbie = !mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE);
> > @@ -522,7 +522,7 @@ static void
> > pSeries_lpar_flush_hash_range(unsigned long number, int local)
> >  	unsigned long flags = 0;
> >  	struct ppc64_tlb_batch *batch =
> > this_cpu_ptr(&ppc64_tlb_batch);
> >  	int lock_tlbie = !mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE);
> > -	unsigned long param[9];
> > +	unsigned long param[PLPAR_HCALL9_BUFSIZE];
> >  	unsigned long hash, index, shift, hidx, slot;
> >  	real_pte_t pte;
> >  	int psize, ssize;
> > -- 
> > 2.7.4