tmpfs,ceph,gfs2,isofs,reiserfs,xfs: fix fh_len checking

Fuzzing with trinity oopsed on the 1st instruction of shmem_fh_to_dentry(),
	u64 inum = fid->raw[2];
which is unhelpfully reported as at the end of shmem_alloc_inode():

BUG: unable to handle kernel paging request at ffff880061cd3000
IP: [<ffffffff812190d0>] shmem_alloc_inode+0x40/0x40
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Call Trace:
 [<ffffffff81488649>] ? exportfs_decode_fh+0x79/0x2d0
 [<ffffffff812d77c3>] do_handle_open+0x163/0x2c0
 [<ffffffff812d792c>] sys_open_by_handle_at+0xc/0x10
 [<ffffffff83a5f3f8>] tracesys+0xe1/0xe6

Right, tmpfs is being stupid to access fid->raw[2] before validating that
fh_len includes it: the buffer kmalloc'ed by do_sys_name_to_handle() may
fall at the end of a page, and the next page not be present.

But some other filesystems (ceph, gfs2, isofs, reiserfs, xfs) are being
careless about fh_len too, in fh_to_dentry() and/or fh_to_parent(), and
could oops in the same way: add the missing fh_len checks to those.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Sage Weil <sage@inktank.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 14 insertions, 4 deletions

diff --git a/fs/ceph/export.c b/fs/ceph/export.c
index 8e1b60e557b6..02ce90972d81 100644
--- a/fs/ceph/export.c
+++ b/fs/ceph/export.c
@@ -99,7 +99,7 @@ static int ceph_encode_fh(struct inode *inode, u32 *rawfh, int *max_len,
  * FIXME: we should try harder by querying the mds for the ino.
  */
 static struct dentry *__fh_to_dentry(struct super_block *sb,
-				     struct ceph_nfs_fh *fh)
+				     struct ceph_nfs_fh *fh, int fh_len)
 {
 	struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 	struct inode *inode;
@@ -107,6 +107,9 @@ static struct dentry *__fh_to_dentry(struct super_block *sb,
 	struct ceph_vino vino;
 	int err;
 
+	if (fh_len < sizeof(*fh) / 4)
+		return ERR_PTR(-ESTALE);
+
 	dout("__fh_to_dentry %llx\n", fh->ino);
 	vino.ino = fh->ino;
 	vino.snap = CEPH_NOSNAP;
@@ -150,7 +153,7 @@ static struct dentry *__fh_to_dentry(struct super_block *sb,
  * convert connectable fh to dentry
  */
 static struct dentry *__cfh_to_dentry(struct super_block *sb,
-				      struct ceph_nfs_confh *cfh)
+				      struct ceph_nfs_confh *cfh, int fh_len)
 {
 	struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 	struct inode *inode;
@@ -158,6 +161,9 @@ static struct dentry *__cfh_to_dentry(struct super_block *sb,
 	struct ceph_vino vino;
 	int err;
 
+	if (fh_len < sizeof(*cfh) / 4)
+		return ERR_PTR(-ESTALE);
+
 	dout("__cfh_to_dentry %llx (%llx/%x)\n",
 	     cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 
@@ -207,9 +213,11 @@ static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 					int fh_len, int fh_type)
 {
 	if (fh_type == 1)
-		return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
+		return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw,
+								fh_len);
 	else
-		return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
+		return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw,
+								fh_len);
 }
 
 /*
@@ -230,6 +238,8 @@ static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 
 	if (fh_type == 1)
 		return ERR_PTR(-ESTALE);
+	if (fh_len < sizeof(*cfh) / 4)
+		return ERR_PTR(-ESTALE);
 
 	pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 		 cfh->parent_name_hash);