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, 4 insertions, 0 deletions

diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
index e8ed6d4a6181..4767774a5f3e 100644
--- a/fs/gfs2/export.c
+++ b/fs/gfs2/export.c
@@ -161,6 +161,8 @@ static struct dentry *gfs2_fh_to_dentry(struct super_block *sb, struct fid *fid,
         case GFS2_SMALL_FH_SIZE:
         case GFS2_LARGE_FH_SIZE:
         case GFS2_OLD_FH_SIZE:
+                if (fh_len < GFS2_SMALL_FH_SIZE)
+                        return NULL;
                 this.no_formal_ino = ((u64)be32_to_cpu(fh[0])) << 32;
                 this.no_formal_ino |= be32_to_cpu(fh[1]);
                 this.no_addr = ((u64)be32_to_cpu(fh[2])) << 32;
@@ -180,6 +182,8 @@ static struct dentry *gfs2_fh_to_parent(struct super_block *sb, struct fid *fid,
         switch (fh_type) {
         case GFS2_LARGE_FH_SIZE:
         case GFS2_OLD_FH_SIZE:
+                if (fh_len < GFS2_LARGE_FH_SIZE)
+                        return NULL;
                 parent.no_formal_ino = ((u64)be32_to_cpu(fh[4])) << 32;
                 parent.no_formal_ino |= be32_to_cpu(fh[5]);
                 parent.no_addr = ((u64)be32_to_cpu(fh[6])) << 32;