[PATCH 5.4 144/152] xfs: clear kernel only flags in XFS_IOC_ATTRMULTI_BY_HANDLE

Greg Kroah-Hartman
2020-03-03T17:58:17Z

From: Christoph Hellwig <hch@lst.de>

commit 953aa9d136f53e226448dbd801a905c28f8071bf upstream.

Don't allow passing arbitrary flags as they change behavior including
memory allocation that the call stack is not prepared for.

Fixes: ddbca70cc45c ("xfs: allocate xattr buffer on demand")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/xfs/libxfs/xfs_attr.h | 7 +++++--
fs/xfs/xfs_ioctl.c | 2 ++
fs/xfs/xfs_ioctl32.c | 2 ++
3 files changed, 9 insertions(+), 2 deletions(-)

--- a/fs/xfs/libxfs/xfs_attr.h
+++ b/fs/xfs/libxfs/xfs_attr.h
@@ -26,7 +26,7 @@ struct xfs_attr_list_context;
*========================================================================*/

-#define ATTR_DONTFOLLOW 0x0001 /* -- unused, from IRIX -- */
+#define ATTR_DONTFOLLOW 0x0001 /* -- ignored, from IRIX -- */
#define ATTR_ROOT 0x0002 /* use attrs in root (trusted) namespace */
#define ATTR_TRUST 0x0004 /* -- unused, from IRIX -- */
#define ATTR_SECURE 0x0008 /* use attrs in security namespace */
@@ -37,7 +37,10 @@ struct xfs_attr_list_context;
#define ATTR_KERNOVAL 0x2000 /* [kernel] get attr size only, not value */

#define ATTR_INCOMPLETE 0x4000 /* [kernel] return INCOMPLETE attr keys */
-#define ATTR_ALLOC 0x8000 /* allocate xattr buffer on demand */
+#define ATTR_ALLOC 0x8000 /* [kernel] allocate xattr buffer on demand */
+
+#define ATTR_KERNEL_FLAGS \
+ (ATTR_KERNOTIME | ATTR_KERNOVAL | ATTR_INCOMPLETE | ATTR_ALLOC)

#define XFS_ATTR_FLAGS \
{ ATTR_DONTFOLLOW, "DONTFOLLOW" }, \
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -536,6 +536,8 @@ xfs_attrmulti_by_handle(

error = 0;
for (i = 0; i < am_hreq.opcount; i++) {
+ ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;
+
ops[i].am_error = strncpy_from_user((char *)attr_name,
ops[i].am_attrname, MAXNAMELEN);
if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
--- a/fs/xfs/xfs_ioctl32.c
+++ b/fs/xfs/xfs_ioctl32.c
@@ -450,6 +450,8 @@ xfs_compat_attrmulti_by_handle(

error = 0;
for (i = 0; i < am_hreq.opcount; i++) {
+ ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;
+
ops[i].am_error = strncpy_from_user((char *)attr_name,
compat_ptr(ops[i].am_attrname),
MAXNAMELEN);