Re: CVE-2014-8159 kernel: infiniband: uverbs: unprotected physical memory access

Yann Droneaud
2015-04-02T15:15:52Z

Hi,
Le jeudi 02 avril 2015 à 10:52 +0000, Shachar Raindel a écrit :
> > -----Original Message-----
> > From: Yann Droneaud [mailto:ydroneaud@opteya.com]
> > Sent: Thursday, April 02, 2015 1:05 PM
> > Le mercredi 18 mars 2015 à 17:39 +0000, Shachar Raindel a écrit :
...
> > > + /*
> > > + * If the combination of the addr and size requested for this
> > memory
> > > + * region causes an integer overflow, return error.
> > > + */
> > > + if ((PAGE_ALIGN(addr + size) <= size) ||
> > > + (PAGE_ALIGN(addr + size) <= addr))
> > > + return ERR_PTR(-EINVAL);
> > > +
> >
> > Can access_ok() be used here ?
> >
> > if (!access_ok(writable ? VERIFY_WRITE : VERIFY_READ,
> > addr, size))
> > return ERR_PTR(-EINVAL);
> >
>
> No, this will break the current ODP semantics.
>
> ODP allows the user to register memory that is not accessible yet.
> This is a critical design feature, as it allows avoiding holding
> a registration cache. Adding this check will break the behavior,
> forcing memory to be all accessible when registering an ODP MR.
>

Failed to notice previously, but since this would break ODP, and ODP is
only available starting v3.19-rc1, my proposed fix might be applicable
for older kernel (if not better).

From 2a3beaeb4b35d968f127cb59cfda2f12dbd87e4b Mon Sep 17 00:00:00 2001
From: Yann Droneaud <ydroneaud@opteya.com>
Date: Thu, 2 Apr 2015 17:01:05 +0200
Subject: [RFC PATCH] IB/core: reject invalid userspace memory range registration

Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
---
drivers/infiniband/core/umem.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index df0c4f605a21..6758b4ac56eb 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -90,6 +90,7 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
DEFINE_DMA_ATTRS(attrs);
struct scatterlist *sg, *sg_list_start;
int need_release = 0;
+ bool writable;

if (dmasync)
dma_set_attr(DMA_ATTR_WRITE_BARRIER, &attrs);
@@ -97,6 +98,19 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
if (!can_do_mlock())
return ERR_PTR(-EPERM);

+ /*
+ * We ask for writable memory if any access flags other than
+ * "remote read" are set. "Local write" and "remote write"
+ * obviously require write access. "Remote atomic" can do
+ * things like fetch and add, which will modify memory, and
+ * "MW bind" can change permissions by binding a window.
+ */
+ writable = !!(access & ~IB_ACCESS_REMOTE_READ);
+
+ if (!access_ok(writable ? VERIFY_WRITE : VERIFY_READ,
+ (void __user *)addr, size))
+ return ERR_PTR(-EFAULT);
+
umem = kzalloc(sizeof *umem, GFP_KERNEL);
if (!umem)
return ERR_PTR(-ENOMEM);
@@ -106,14 +120,7 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
umem->offset = addr & ~PAGE_MASK;
umem->page_size = PAGE_SIZE;
umem->pid = get_task_pid(current, PIDTYPE_PID);
- /*
- * We ask for writable memory if any access flags other than
- * "remote read" are set. "Local write" and "remote write"
- * obviously require write access. "Remote atomic" can do
- * things like fetch and add, which will modify memory, and
- * "MW bind" can change permissions by binding a window.
- */
- umem->writable = !!(access & ~IB_ACCESS_REMOTE_READ);
+ umem->writable = writable;

/* We assume the memory is from hugetlb until proved otherwise */
umem->hugetlb = 1;
--
2.1.0

Regards.

--
Yann Droneaud
OPTEYA