Patch "RDMA/cxgb4: add missing padding at end of struct c4iw_alloc_ucontext_resp" has been added to the 3.15-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



This is a note to let you know that I've just added the patch titled

    RDMA/cxgb4: add missing padding at end of struct c4iw_alloc_ucontext_resp

to the 3.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rdma-cxgb4-add-missing-padding-at-end-of-struct-c4iw_alloc_ucontext_resp.patch
and it can be found in the queue-3.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From b7dfa8895f64ffa371d0ed09c1d1ba8c6e19b956 Mon Sep 17 00:00:00 2001
From: Yann Droneaud <ydroneaud@xxxxxxxxxx>
Date: Mon, 5 May 2014 19:35:26 +0200
Subject: RDMA/cxgb4: add missing padding at end of struct c4iw_alloc_ucontext_resp

From: Yann Droneaud <ydroneaud@xxxxxxxxxx>

commit b7dfa8895f64ffa371d0ed09c1d1ba8c6e19b956 upstream.

The i386 ABI disagrees with most other ABIs regarding alignment of
data types larger than 4 bytes: on most ABIs a padding must be added
at end of the structures, while it is not required on i386.

So for most ABI struct c4iw_alloc_ucontext_resp gets implicitly padded
to be aligned on a 8 bytes multiple, while for i386, such padding is
not added.

The tool pahole can be used to find such implicit padding:

  $ pahole --anon_include \
           --nested_anon_include \
           --recursive \
           --class_name c4iw_alloc_ucontext_resp \
           drivers/infiniband/hw/cxgb4/iw_cxgb4.o

Then, structure layout can be compared between i386 and x86_64:

#  +++ obj-i386/drivers/infiniband/hw/cxgb4/iw_cxgb4.o.pahole.txt   2014-03-28 11:43:05.547432195 +0100
#  --- obj-x86_64/drivers/infiniband/hw/cxgb4/iw_cxgb4.o.pahole.txt 2014-03-28 10:55:10.990133017 +0100
#  @@ -2,9 +2,8 @@ struct c4iw_alloc_ucontext_resp {
#          __u64                      status_page_key;      /*     0     8 */
#          __u32                      status_page_size;     /*     8     4 */
#
#  -       /* size: 12, cachelines: 1, members: 2 */
#  -       /* last cacheline: 12 bytes */
#  +       /* size: 16, cachelines: 1, members: 2 */
#  +       /* padding: 4 */
#  +       /* last cacheline: 16 bytes */
#   };

This ABI disagreement will make an x86_64 kernel try to write past the
buffer provided by an i386 binary.

When boundary check will be implemented, the x86_64 kernel will refuse
to write past the i386 userspace provided buffer and the uverbs will
fail.

If the structure is on a page boundary and the next page is not
mapped, ib_copy_to_udata() will fail and the uverb will fail.

Additionally, as reported by Dan Carpenter, without the implicit
padding being properly cleared, an information leak would take place
in most architectures.

This patch adds an explicit padding to struct c4iw_alloc_ucontext_resp,
and, like 92b0ca7cb149 ("IB/mlx5: Fix stack info leak in
mlx5_ib_alloc_ucontext()"), makes function c4iw_alloc_ucontext()
not writting this padding field to userspace. This way, x86_64 kernel
will be able to write struct c4iw_alloc_ucontext_resp as expected by
unpatched and patched i386 libcxgb4.

Link: http://marc.info/?i=cover.1399309513.git.ydroneaud@xxxxxxxxxx
Link: http://marc.info/?i=1395848977.3297.15.camel@localhost.localdomain
Link: http://marc.info/?i=20140328082428.GH25192@mwanda
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 05eb23893c2c ("cxgb4/iw_cxgb4: Doorbell Drop Avoidance Bug Fixes")
Reported-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
Acked-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Roland Dreier <roland@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/hw/cxgb4/provider.c |    5 +++--
 drivers/infiniband/hw/cxgb4/user.h     |    1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/hw/cxgb4/provider.c
+++ b/drivers/infiniband/hw/cxgb4/provider.c
@@ -122,7 +122,7 @@ static struct ib_ucontext *c4iw_alloc_uc
 	INIT_LIST_HEAD(&context->mmaps);
 	spin_lock_init(&context->mmap_lock);
 
-	if (udata->outlen < sizeof(uresp)) {
+	if (udata->outlen < sizeof(uresp) - sizeof(uresp.reserved)) {
 		if (!warned++)
 			pr_err(MOD "Warning - downlevel libcxgb4 (non-fatal), device status page disabled.");
 		rhp->rdev.flags |= T4_STATUS_PAGE_DISABLED;
@@ -140,7 +140,8 @@ static struct ib_ucontext *c4iw_alloc_uc
 		context->key += PAGE_SIZE;
 		spin_unlock(&context->mmap_lock);
 
-		ret = ib_copy_to_udata(udata, &uresp, sizeof(uresp));
+		ret = ib_copy_to_udata(udata, &uresp,
+				       sizeof(uresp) - sizeof(uresp.reserved));
 		if (ret)
 			goto err_mm;
 
--- a/drivers/infiniband/hw/cxgb4/user.h
+++ b/drivers/infiniband/hw/cxgb4/user.h
@@ -75,5 +75,6 @@ struct c4iw_create_qp_resp {
 struct c4iw_alloc_ucontext_resp {
 	__u64 status_page_key;
 	__u32 status_page_size;
+	__u32 reserved; /* explicit padding (optional for i386) */
 };
 #endif


Patches currently in stable-queue which might be from ydroneaud@xxxxxxxxxx are

queue-3.15/rdma-cxgb4-add-missing-padding-at-end-of-struct-c4iw_alloc_ucontext_resp.patch
queue-3.15/rdma-cxgb4-add-missing-padding-at-end-of-struct-c4iw_create_cq_resp.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]