linux-kernel - [ 137/143] xfs: underflow bug in xfs_attrlist_by

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Date:	Mon, 12 May 2014 02:34:17 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Dan Carpenter <dan.carpenter@...cle.com>, Ben Myers <bpm@....com>,
	Willy Tarreau <w@....eu>
Subject: [ 137/143] xfs: underflow bug in xfs_attrlist_by_handle()

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@...cle.com>

If we allocate less than sizeof(struct attrlist) then we end up
corrupting memory or doing a ZERO_PTR_SIZE dereference.

This can only be triggered with CAP_SYS_ADMIN.

Reported-by: Nico Golde <nico@...lde.de>
Reported-by: Fabian Yamaguchi <fabs@...sec.de>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Reviewed-by: Dave Chinner <dchinner@...hat.com>
Signed-off-by: Ben Myers <bpm@....com>

(cherry picked from commit 071c529eb672648ee8ca3f90944bcbcc730b4c06)
[dannf: backported to Debian's 2.6.32]
Signed-off-by: Willy Tarreau <w@....eu>
---
 fs/xfs/linux-2.6/xfs_ioctl.c   | 3 ++-
 fs/xfs/linux-2.6/xfs_ioctl32.c | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
index 942362f..5663351 100644
--- a/fs/xfs/linux-2.6/xfs_ioctl.c
+++ b/fs/xfs/linux-2.6/xfs_ioctl.c
@@ -410,7 +410,8 @@ xfs_attrlist_by_handle(
 		return -XFS_ERROR(EPERM);
 	if (copy_from_user(&al_hreq, arg, sizeof(xfs_fsop_attrlist_handlereq_t)))
 		return -XFS_ERROR(EFAULT);
-	if (al_hreq.buflen > XATTR_LIST_MAX)
+	if (al_hreq.buflen < sizeof(struct attrlist) ||
+	    al_hreq.buflen > XATTR_LIST_MAX)
 		return -XFS_ERROR(EINVAL);
 
 	/*
diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
index bad485a..782d03d 100644
--- a/fs/xfs/linux-2.6/xfs_ioctl32.c
+++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
@@ -361,8 +361,8 @@ xfs_compat_attrlist_by_handle(
 	if (copy_from_user(&al_hreq, arg,
 			   sizeof(compat_xfs_fsop_attrlist_handlereq_t)))
 		return -XFS_ERROR(EFAULT);
-	if (al_hreq.buflen > XATTR_LIST_MAX)
-		return -XFS_ERROR(EINVAL);
+	if (al_hreq.buflen < sizeof(struct attrlist) ||
+	    al_hreq.buflen > XATTR_LIST_MAX)
 
 	/*
 	 * Reject flags, only allow namespaces.
-- 
1.7.12.2.21.g234cd45.dirty



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