[PATCH AUTOSEL 5.4 056/330] gfs2: clean up iopen glock mess in gfs2_create_inode

Sasha Levin
2020-09-18T03:11:50Z

From: Bob Peterson <rpeterso@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 <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@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 8466166f22e3d..988bb7b17ed8f 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -712,7 +712,7 @@ 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;
@@ -723,7 +723,7 @@ 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));

@@ -732,7 +732,6 @@ 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);

@@ -765,6 +764,8 @@ 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);
@@ -772,15 +773,15 @@ 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