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Re: [PATCH V2] xfs: zero proper structure size for geometry calls

To: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>
Subject: Re: [PATCH V2] xfs: zero proper structure size for geometry calls
From: Jeffrey Hundstad <jeffrey.hundstad@xxxxxxxx>
Date: Tue, 01 Mar 2011 09:36:44 -0600
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, Eugene Teo <eugeneteo@xxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <1298984132.32568.3.camel@dan>
References: <4D6C28A5.60905@xxxxxxxx> <4D6C4DEE.6020902@xxxxxxxxxxx> <4D6C9958.2040607@xxxxxxxxxxx> <1298984132.32568.3.camel@dan>
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.16) Gecko/20101227 Icedove/3.0.11


On 03/01/2011 06:55 AM, Dan Rosenberg wrote:
On Tue, 2011-03-01 at 00:59 -0600, Eric Sandeen wrote:
commit 493f3358cb289ccf716c5a14fa5bb52ab75943e5 added:

+       memset(geo, 0, sizeof(*geo));

but unfortunately we're dealing with a cast pointer here, and
the caller may actually have a smaller structure on the stack.
Zeroing out more leads to stack corruption traps:

Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: 
f87aca93

Pid: 262, comm: xfs_fsr Not tainted 2.6.38-rc6-493f3358cb2+ #1
Call Trace:

[<c12991ac>] ? panic+0x50/0x150
[<c102ed71>] ? __stack_chk_fail+0x10/0x18
[<f87aca93>] ? xfs_ioc_fsgeometry_v1+0x56/0x5d [xfs]

Fix this by zeroing out the structure in the callers, where we know
the actual size.
Thanks for catching this early, and sorry for the misstep.

Reviewed-by: Dan Rosenberg<drosenberg@xxxxxxxxxxxxx>

Reported-by: Jeffrey Hundstad<jeffrey.hundstad@xxxxxxxx>
Signed-off-by: Eric Sandeen<sandeen@xxxxxxxxxx>
---

V2: Use sizeof (variable) not sizeof (type)

diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
index f5e2a19..871e5f0 100644
--- a/fs/xfs/linux-2.6/xfs_ioctl.c
+++ b/fs/xfs/linux-2.6/xfs_ioctl.c
@@ -698,6 +698,7 @@ xfs_ioc_fsgeometry_v1(
        xfs_fsop_geom_v1_t      fsgeo;
        int                     error;

+       memset(&fsgeo, 0, sizeof(fsgeo));
        error = xfs_fs_geometry(mp, (xfs_fsop_geom_t *)&fsgeo, 3);
        if (error)
                return -error;
@@ -715,6 +716,7 @@ xfs_ioc_fsgeometry(
        xfs_fsop_geom_t         fsgeo;
        int                     error;

+       memset(&fsgeo, 0, sizeof(fsgeo));
        error = xfs_fs_geometry(mp,&fsgeo, 4);
        if (error)
                return -error;
diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
index b3486df..f25d38e 100644
--- a/fs/xfs/linux-2.6/xfs_ioctl32.c
+++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
@@ -73,6 +73,7 @@ xfs_compat_ioc_fsgeometry_v1(
        xfs_fsop_geom_t           fsgeo;
        int                       error;

+       memset(&fsgeo, 0, sizeof(fsgeo));
        error = xfs_fs_geometry(mp,&fsgeo, 3);
        if (error)
                return -error;
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 85668ef..cec89dd 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -53,9 +53,6 @@ xfs_fs_geometry(
        xfs_fsop_geom_t         *geo,
        int                     new_version)
  {
-
-       memset(geo, 0, sizeof(*geo));
-
        geo->blocksize = mp->m_sb.sb_blocksize;
        geo->rtextsize = mp->m_sb.sb_rextsize;
        geo->agblocks = mp->m_sb.sb_agblocks;



Hello,

I confirm that this patch DOES FIX the problem I was seeing with xfs_fsr that caused a hit on the stack-protector.

Thanks for your hard work!

Tested-by: Jeffrey Hundstad <jeffrey.hundstad@xxxxxxxx>

--
Jeffrey Hundstad

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