From b10cdcdc2012b2c199077a0a648e8a7067e573bf Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@gmail.com>
Date: Mon, 8 Oct 2018 07:25:23 +0300
Subject: [PATCH] ovl: untangle copy up call chain
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@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/overlayfs/copy_up.c | 245 ++++++++++++++++++++++++++---------------
1 file changed, 159 insertions(+), 86 deletions(-)
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 989782a0c0c97..618cffc14f914 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;
@@ -440,62 +439,6 @@ 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)
-{
- int err;
- struct dentry *upper;
- struct inode *udir = d_inode(c->destdir);
-
- upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
- 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);
-
- if (!err)
- *newdentry = dget(c->tmpfile ? upper : temp);
- dput(upper);
-
- return err;
-}
-
-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;
- struct ovl_cattr cattr = {
- /* Can't properly set mode on creation because of the umask */
- .mode = c->stat.mode & S_IFMT,
- .rdev = c->stat.rdev,
- .link = c->link
- };
-
- err = security_inode_copy_up(c->dentry, &new_creds);
- if (err < 0)
- return ERR_PTR(err);
-
- 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);
-
- if (new_creds) {
- revert_creds(old_creds);
- put_cred(new_creds);
- }
-
- return temp;
-}
-
static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
{
int err;
@@ -547,37 +490,94 @@ 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)
+static struct dentry *ovl_get_workdir_temp(struct ovl_copy_up_ctx *c)
+{
+ int err;
+ struct dentry *temp;
+ const struct cred *old_creds = NULL;
+ struct cred *new_creds = NULL;
+ struct ovl_cattr cattr = {
+ /* Can't properly set mode on creation because of the umask */
+ .mode = c->stat.mode & S_IFMT,
+ .rdev = c->stat.rdev,
+ .link = c->link
+ };
+
+ err = security_inode_copy_up(c->dentry, &new_creds);
+ if (err < 0)
+ return ERR_PTR(err);
+
+ if (new_creds)
+ old_creds = override_creds(new_creds);
+
+ temp = ovl_create_temp(c->workdir, &cattr);
+
+ if (new_creds) {
+ revert_creds(old_creds);
+ put_cred(new_creds);
+ }
+
+ return temp;
+}
+
+/*
+ * 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;
+ struct inode *udir = d_inode(c->destdir);
+
+ upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
+ if (IS_ERR(upper))
+ return PTR_ERR(upper);
+
+ err = ovl_do_rename(d_inode(c->workdir), temp, udir, upper, 0);
+ if (!err)
+ *newdentry = dget(temp);
+ dput(upper);
+
+ return err;
+}
+
+/*
+ * Copyup using workdir to prepare temp file. Used when copying up directories,
+ * special files or 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 unlock;
err = ovl_copy_up_inode(c, temp);
if (err)
- goto out;
+ goto cleanup;
if (S_ISDIR(c->stat.mode) && c->indexed) {
err = ovl_create_index(c->dentry, c->lowerpath.dentry, temp);
if (err)
- goto out;
+ goto 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 cleanup;
if (!c->metacopy)
ovl_set_upperdata(d_inode(c->dentry));
@@ -585,13 +585,94 @@ static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c)
ovl_inode_update(inode, newdentry);
if (S_ISDIR(inode->i_mode))
ovl_set_flag(OVL_WHITEOUTS, inode);
+out_dput:
+ dput(temp);
+unlock:
+ unlock_rename(c->workdir, c->destdir);
+
+ return err;
+
+cleanup:
+ ovl_cleanup(d_inode(c->workdir), temp);
+ goto out_dput;
+}
+
+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);
+ if (err < 0)
+ return ERR_PTR(err);
+
+ if (new_creds)
+ old_creds = override_creds(new_creds);
+
+ temp = ovl_do_tmpfile(c->workdir, c->stat.mode);
+
+ if (new_creds) {
+ revert_creds(old_creds);
+ put_cred(new_creds);
+ }
+
+ return temp;
+}
+
+/* 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;
+ 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 unlock;
+
+ err = ovl_do_link(temp, udir, upper);
+ if (!err)
+ *newdentry = dget(upper);
+ dput(upper);
+
+unlock:
+ inode_unlock(udir);
+
+ 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:
- if (err && !c->tmpfile)
- ovl_cleanup(d_inode(c->workdir), temp);
dput(temp);
return err;
-
}
/*
@@ -645,18 +726,10 @@ 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;
--
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