In an attempt to dedup ~100 LOC, we ended up creating a tangled call
chain, whose branches merge and diverge in several points according to
the immutable c->tmpfile copy up mode.
This call chain was hard to analyse for locking correctness because the
locking requirements for the c->tmpfile flow were very different from
the locking requirements for the !c->tmpfile flow (i.e. directory vs.
regulare file copy up).
Split the copy up helpers of the c->tmpfile flow from those of the
!c->tmpfile (i.e. workdir) flow and remove the c->tmpfile mode from
copy up context.
Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
Miklos,
I've managed to mess up error handling in 3 out of 6 helpers in v1.
Better take a close look that I did not miss more...
Thanks,
Amir.
fs/overlayfs/copy_up.c | 155 ++++++++++++++++++++++++++++++-----------
1 file changed, 114 insertions(+), 41 deletions(-)
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 1cc797a08a5b..78a5049f7a5a 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -395,7 +395,6 @@ struct ovl_copy_up_ctx {
struct dentry *destdir;
struct qstr destname;
struct dentry *workdir;
- bool tmpfile;
bool origin;
bool indexed;
bool metacopy;
@@ -440,8 +439,14 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c)
return err;
}
-static int ovl_install_temp(struct ovl_copy_up_ctx *c, struct dentry *temp,
- struct dentry **newdentry)
+/*
+ * Move temp file from workdir into place on upper dir.
+ * Used when copying up directories and when upper fs doesn't support O_TMPFILE.
+ *
+ * Caller must hold ovl_lock_rename_workdir().
+ */
+static int ovl_rename_temp(struct ovl_copy_up_ctx *c, struct dentry *temp,
+ struct dentry **newdentry)
{
int err;
struct dentry *upper;
@@ -451,19 +456,40 @@ static int ovl_install_temp(struct ovl_copy_up_ctx *c, struct dentry *temp,
if (IS_ERR(upper))
return PTR_ERR(upper);
- if (c->tmpfile)
- err = ovl_do_link(temp, udir, upper);
- else
- err = ovl_do_rename(d_inode(c->workdir), temp, udir, upper, 0);
+ err = ovl_do_rename(d_inode(c->workdir), temp, udir, upper, 0);
+ if (!err)
+ *newdentry = dget(temp);
+ dput(upper);
+ return err;
+}
+
+/* Link O_TMPFILE into place on upper dir */
+static int ovl_link_tmpfile(struct ovl_copy_up_ctx *c, struct dentry *temp,
+ struct dentry **newdentry)
+{
+ int err;
+ struct dentry *upper = NULL;
+ struct inode *udir = d_inode(c->destdir);
+
+ inode_lock_nested(udir, I_MUTEX_PARENT);
+
+ upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
+ err = PTR_ERR(upper);
+ if (IS_ERR(upper))
+ goto out;
+
+ err = ovl_do_link(temp, udir, upper);
if (!err)
- *newdentry = dget(c->tmpfile ? upper : temp);
+ *newdentry = dget(upper);
dput(upper);
+out:
+ inode_unlock(udir);
return err;
}
-static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c)
+static struct dentry *ovl_get_workdir_temp(struct ovl_copy_up_ctx *c)
{
int err;
struct dentry *temp;
@@ -484,10 +510,32 @@ static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c)
if (new_creds)
old_creds = override_creds(new_creds);
- if (c->tmpfile)
- temp = ovl_do_tmpfile(c->workdir, c->stat.mode);
- else
- temp = ovl_create_temp(c->workdir, &cattr);
+ temp = ovl_create_temp(c->workdir, &cattr);
+out:
+ if (new_creds) {
+ revert_creds(old_creds);
+ put_cred(new_creds);
+ }
+
+ return temp;
+}
+
+static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c)
+{
+ int err;
+ struct dentry *temp;
+ const struct cred *old_creds = NULL;
+ struct cred *new_creds = NULL;
+
+ err = security_inode_copy_up(c->dentry, &new_creds);
+ temp = ERR_PTR(err);
+ if (err < 0)
+ goto out;
+
+ if (new_creds)
+ old_creds = override_creds(new_creds);
+
+ temp = ovl_do_tmpfile(c->destdir, c->stat.mode);
out:
if (new_creds) {
revert_creds(old_creds);
@@ -548,37 +596,39 @@ static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
return err;
}
-static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c)
+/*
+ * Copyup using workdir to prepare temp file.
+ * Used when copying up directories and when upper fs doesn't support O_TMPFILE.
+ */
+static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
{
- struct inode *udir = c->destdir->d_inode;
struct inode *inode;
struct dentry *newdentry = NULL;
struct dentry *temp;
int err;
- temp = ovl_get_tmpfile(c);
+ err = ovl_lock_rename_workdir(c->workdir, c->destdir);
+ if (err)
+ return err;
+
+ temp = ovl_get_workdir_temp(c);
+ err = PTR_ERR(temp);
if (IS_ERR(temp))
- return PTR_ERR(temp);
+ goto out;
err = ovl_copy_up_inode(c, temp);
if (err)
- goto out;
+ goto out_cleanup;
if (S_ISDIR(c->stat.mode) && c->indexed) {
err = ovl_create_index(c->dentry, c->lowerpath.dentry, temp);
if (err)
- goto out;
+ goto out_cleanup;
}
- if (c->tmpfile) {
- inode_lock_nested(udir, I_MUTEX_PARENT);
- err = ovl_install_temp(c, temp, &newdentry);
- inode_unlock(udir);
- } else {
- err = ovl_install_temp(c, temp, &newdentry);
- }
+ err = ovl_rename_temp(c, temp, &newdentry);
if (err)
- goto out;
+ goto out_cleanup;
if (!c->metacopy)
ovl_set_upperdata(d_inode(c->dentry));
@@ -587,10 +637,41 @@ static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c)
if (S_ISDIR(inode->i_mode))
ovl_set_flag(OVL_WHITEOUTS, inode);
-out:
- if (err && !c->tmpfile)
+out_cleanup:
+ if (err)
ovl_cleanup(d_inode(c->workdir), temp);
dput(temp);
+out:
+ unlock_rename(c->workdir, c->destdir);
+ return err;
+
+}
+
+/* Copyup using O_TMPFILE which does not require cross dir locking */
+static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)
+{
+ struct dentry *newdentry = NULL;
+ struct dentry *temp;
+ int err;
+
+ temp = ovl_get_tmpfile(c);
+ if (IS_ERR(temp))
+ return PTR_ERR(temp);
+
+ err = ovl_copy_up_inode(c, temp);
+ if (err)
+ goto out;
+
+ err = ovl_link_tmpfile(c, temp, &newdentry);
+ if (err)
+ goto out;
+
+ if (!c->metacopy)
+ ovl_set_upperdata(d_inode(c->dentry));
+ ovl_inode_update(d_inode(c->dentry), newdentry);
+
+out:
+ dput(temp);
return err;
}
@@ -646,18 +727,10 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
}
/* Should we copyup with O_TMPFILE or with workdir? */
- if (S_ISREG(c->stat.mode) && ofs->tmpfile) {
- c->tmpfile = true;
- err = ovl_copy_up_locked(c);
- } else {
- err = ovl_lock_rename_workdir(c->workdir, c->destdir);
- if (!err) {
- err = ovl_copy_up_locked(c);
- unlock_rename(c->workdir, c->destdir);
- }
- }
-
-
+ if (S_ISREG(c->stat.mode) && ofs->tmpfile)
+ err = ovl_copy_up_tmpfile(c);
+ else
+ err = ovl_copy_up_workdir(c);
if (err)
goto out;
--
2.17.1
