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ovl: fix oopses in ovl_fill_super() failure paths

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ovl_free_fs() dereferences ofs->workbasedir and ofs->upper_mnt in cases when
those might not have been initialized yet.

Fix the initialization order for these fields.

Reported-by: syzbot+c75f181dc8429d2eb887@syzkaller.appspotmail.com
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc:  <stable@vger.kernel.org> # v4.15
Fixes: 95e6d4177c ("ovl: grab reference to workbasedir early")
Fixes: a9075cdb46 ("ovl: factor out ovl_free_fs() helper")
This commit is contained in:
Miklos Szeredi 2018-09-10 11:43:29 +02:00
parent b833a36603
commit 8c25741aaa
1 changed files with 14 additions and 12 deletions
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26
fs/overlayfs/super.c
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@ -982,16 +982,6 @@ static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
if (err)
goto out;
err = -EBUSY;
if (ovl_inuse_trylock(upperpath->dentry)) {
ofs->upperdir_locked = true;
} else if (ofs->config.index) {
pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
goto out;
} else {
pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
}
upper_mnt = clone_private_mount(upperpath);
err = PTR_ERR(upper_mnt);
if (IS_ERR(upper_mnt)) {
@ -1002,6 +992,17 @@ static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
/* Don't inherit atime flags */
upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
ofs->upper_mnt = upper_mnt;
err = -EBUSY;
if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
ofs->upperdir_locked = true;
} else if (ofs->config.index) {
pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
goto out;
} else {
pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
}
err = 0;
out:
return err;
@ -1101,8 +1102,10 @@ static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
goto out;
}
ofs->workbasedir = dget(workpath.dentry);
err = -EBUSY;
if (ovl_inuse_trylock(workpath.dentry)) {
if (ovl_inuse_trylock(ofs->workbasedir)) {
ofs->workdir_locked = true;
} else if (ofs->config.index) {
pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
@ -1111,7 +1114,6 @@ static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
}
ofs->workbasedir = dget(workpath.dentry);
err = ovl_make_workdir(ofs, &workpath);
if (err)
goto out;