[PATCH AUTOSEL 4.19 035/206] gfs2: clean up iopen glock mess in gfs2_create_inode

[Sasha Levin]

From: Bob Peterson <rpete...@redhat.com>

[ Upstream commit 2c47c1be51fbded1f7baa2ceaed90f97932f79be ]

Before this patch, gfs2_create_inode had a use-after-free for the
iopen glock in some error paths because it did this:

        gfs2_glock_put(io_gl);
fail_gunlock2:
        if (io_gl)
                clear_bit(GLF_INODE_CREATING, &io_gl->gl_flags);

In some cases, the io_gl was used for create and only had one
reference, so the glock might be freed before the clear_bit().
This patch tries to straighten it out by only jumping to the
error paths where iopen is properly set, and moving the
gfs2_glock_put after the clear_bit.

Signed-off-by: Bob Peterson <rpete...@redhat.com>
Signed-off-by: Andreas Gruenbacher <agrue...@redhat.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 fs/gfs2/inode.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index d968b5c5df217..a52b8b0dceeb9 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -715,7 +715,7 @@ static int gfs2_create_inode(struct inode *dir, struct 
dentry *dentry,
 
        error = gfs2_trans_begin(sdp, blocks, 0);
        if (error)
-               goto fail_gunlock2;
+               goto fail_free_inode;
 
        if (blocks > 1) {
                ip->i_eattr = ip->i_no_addr + 1;
@@ -726,7 +726,7 @@ static int gfs2_create_inode(struct inode *dir, struct 
dentry *dentry,
 
        error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, 
&io_gl);
        if (error)
-               goto fail_gunlock2;
+               goto fail_free_inode;
 
        BUG_ON(test_and_set_bit(GLF_INODE_CREATING, &io_gl->gl_flags));
 
@@ -735,7 +735,6 @@ static int gfs2_create_inode(struct inode *dir, struct 
dentry *dentry,
                goto fail_gunlock2;
 
        glock_set_object(ip->i_iopen_gh.gh_gl, ip);
-       gfs2_glock_put(io_gl);
        gfs2_set_iop(inode);
        insert_inode_hash(inode);
 
@@ -768,6 +767,8 @@ static int gfs2_create_inode(struct inode *dir, struct 
dentry *dentry,
 
        mark_inode_dirty(inode);
        d_instantiate(dentry, inode);
+       /* After instantiate, errors should result in evict which will destroy
+        * both inode and iopen glocks properly. */
        if (file) {
                file->f_mode |= FMODE_CREATED;
                error = finish_open(file, dentry, gfs2_open_common);
@@ -775,15 +776,15 @@ static int gfs2_create_inode(struct inode *dir, struct 
dentry *dentry,
        gfs2_glock_dq_uninit(ghs);
        gfs2_glock_dq_uninit(ghs + 1);
        clear_bit(GLF_INODE_CREATING, &io_gl->gl_flags);
+       gfs2_glock_put(io_gl);
        return error;
 
 fail_gunlock3:
        glock_clear_object(io_gl, ip);
        gfs2_glock_dq_uninit(&ip->i_iopen_gh);
-       gfs2_glock_put(io_gl);
 fail_gunlock2:
-       if (io_gl)
-               clear_bit(GLF_INODE_CREATING, &io_gl->gl_flags);
+       clear_bit(GLF_INODE_CREATING, &io_gl->gl_flags);
+       gfs2_glock_put(io_gl);
 fail_free_inode:
        if (ip->i_gl) {
                glock_clear_object(ip->i_gl, ip);
-- 
2.25.1