[3.16.y-ckt stable] Patch "IB/core: don't disallow registering region starting at 0x0" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    IB/core: don't disallow registering region starting at 0x0

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt11.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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>From a77695d7a077d6995f7f9c1cac2b6c5730577b4d Mon Sep 17 00:00:00 2001
From: Yann Droneaud <ydroneaud at opteya.com>
Date: Mon, 13 Apr 2015 14:56:23 +0200
Subject: IB/core: don't disallow registering region starting at 0x0

commit 66578b0b2f69659f00b6169e6fe7377c4b100d18 upstream.

In a call to ib_umem_get(), if address is 0x0 and size is
already page aligned, check added in commit 8494057ab5e4
("IB/uverbs: Prevent integer overflow in ib_umem_get address
arithmetic") will refuse to register a memory region that
could otherwise be valid (provided vm.mmap_min_addr sysctl
and mmap_low_allowed SELinux knobs allow userspace to map
something at address 0x0).

This patch allows back such registration: ib_umem_get()
should probably don't care of the base address provided it
can be pinned with get_user_pages().

There's two possible overflows, in (addr + size) and in
PAGE_ALIGN(addr + size), this patch keep ensuring none
of them happen while allowing to pin memory at address
0x0. Anyway, the case of size equal 0 is no more (partially)
handled as 0-length memory region are disallowed by an
earlier check.

Link: http://mid.gmane.org/cover.1428929103.git.ydroneaud@opteya.com
Cc: Shachar Raindel <raindel at mellanox.com>
Cc: Jack Morgenstein <jackm at mellanox.com>
Cc: Or Gerlitz <ogerlitz at mellanox.com>
Signed-off-by: Yann Droneaud <ydroneaud at opteya.com>
Reviewed-by: Sagi Grimberg <sagig at mellanox.com>
Reviewed-by: Haggai Eran <haggaie at mellanox.com>
Signed-off-by: Doug Ledford <dledford at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/infiniband/core/umem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 9cc7af4bca94..c9fed8f2e070 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -101,8 +101,8 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
 	 * 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))
+	if (((addr + size) < addr) ||
+	    PAGE_ALIGN(addr + size) < (addr + size))
 		return ERR_PTR(-EINVAL);

 	if (!can_do_mlock())