ovl: factor out ovl_check_origin_fh()

Re-factor ovl_check_origin() and ovl_get_origin(), so origin fh xattr is
read from upper inode only once during lookup with multiple lower layers
and only once when verifying index entry origin.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index a38db76cbccd8efcdf2184d1a262caef310c733f..a6b9bd2afca1656b3a3781d564f23f5a473c6467 100644 (file)
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -87,9 +87,36 @@ static int ovl_acceptable(void *ctx, struct dentry *dentry)
        return 1;
 }
 
+/*
+ * Check validity of an overlay file handle buffer.
+ *
+ * Return 0 for a valid file handle.
+ * Return -ENODATA for "origin unknown".
+ * Return <0 for an invalid file handle.
+ */
+static int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
+{
+       if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len)
+               return -EINVAL;
+
+       if (fh->magic != OVL_FH_MAGIC)
+               return -EINVAL;
+
+       /* Treat larger version and unknown flags as "origin unknown" */
+       if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
+               return -ENODATA;
+
+       /* Treat endianness mismatch as "origin unknown" */
+       if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
+           (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
+               return -ENODATA;
+
+       return 0;
+}
+
 static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
 {
-       int res;
+       int res, err;
        struct ovl_fh *fh = NULL;
 
        res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
@@ -102,7 +129,7 @@ static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
        if (res == 0)
                return NULL;
 
-       fh  = kzalloc(res, GFP_KERNEL);
+       fh = kzalloc(res, GFP_KERNEL);
        if (!fh)
                return ERR_PTR(-ENOMEM);
 
@@ -110,20 +137,12 @@ static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
        if (res < 0)
                goto fail;
 
-       if (res < sizeof(struct ovl_fh) || res < fh->len)
-               goto invalid;
-
-       if (fh->magic != OVL_FH_MAGIC)
+       err = ovl_check_fh_len(fh, res);
+       if (err < 0) {
+               if (err == -ENODATA)
+                       goto out;
                goto invalid;
-
-       /* Treat larger version and unknown flags as "origin unknown" */
-       if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
-               goto out;
-
-       /* Treat endianness mismatch as "origin unknown" */
-       if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
-           (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
-               goto out;
+       }
 
        return fh;
 
@@ -139,22 +158,17 @@ invalid:
        goto out;
 }
 
-static struct dentry *ovl_get_origin(struct dentry *dentry,
-                                    struct vfsmount *mnt)
+static struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
 {
-       struct dentry *origin = NULL;
-       struct ovl_fh *fh = ovl_get_origin_fh(dentry);
+       struct dentry *origin;
        int bytes;
 
-       if (IS_ERR_OR_NULL(fh))
-               return (struct dentry *)fh;
-
        /*
         * Make sure that the stored uuid matches the uuid of the lower
         * layer where file handle will be decoded.
         */
        if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
-               goto out;
+               return NULL;
 
        bytes = (fh->len - offsetof(struct ovl_fh, fid));
        origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
@@ -164,22 +178,15 @@ static struct dentry *ovl_get_origin(struct dentry *dentry,
                /* Treat stale file handle as "origin unknown" */
                if (origin == ERR_PTR(-ESTALE))
                        origin = NULL;
-               goto out;
+               return origin;
        }
 
-       if (ovl_dentry_weird(origin) ||
-           ((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT))
-               goto invalid;
+       if (ovl_dentry_weird(origin)) {
+               dput(origin);
+               return NULL;
+       }
 
-out:
-       kfree(fh);
        return origin;
-
-invalid:
-       pr_warn_ratelimited("overlayfs: invalid origin (%pd2)\n", origin);
-       dput(origin);
-       origin = NULL;
-       goto out;
 }
 
 static bool ovl_is_opaquedir(struct dentry *dentry)
@@ -284,9 +291,9 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 }
 
 
-static int ovl_check_origin(struct dentry *upperdentry,
-                           struct ovl_path *lower, unsigned int numlower,
-                           struct ovl_path **stackp, unsigned int *ctrp)
+static int ovl_check_origin_fh(struct ovl_fh *fh, struct dentry *upperdentry,
+                              struct ovl_path *lower, unsigned int numlower,
+                              struct ovl_path **stackp)
 {
        struct vfsmount *mnt;
        struct dentry *origin = NULL;
@@ -294,18 +301,20 @@ static int ovl_check_origin(struct dentry *upperdentry,
 
        for (i = 0; i < numlower; i++) {
                mnt = lower[i].layer->mnt;
-               origin = ovl_get_origin(upperdentry, mnt);
-               if (IS_ERR(origin))
-                       return PTR_ERR(origin);
-
+               origin = ovl_decode_fh(fh, mnt);
                if (origin)
                        break;
        }
 
        if (!origin)
-               return 0;
+               return -ESTALE;
+       else if (IS_ERR(origin))
+               return PTR_ERR(origin);
+
+       if (!ovl_is_whiteout(upperdentry) &&
+           ((d_inode(origin)->i_mode ^ d_inode(upperdentry)->i_mode) & S_IFMT))
+               goto invalid;
 
-       BUG_ON(*ctrp);
        if (!*stackp)
                *stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL);
        if (!*stackp) {
@@ -313,9 +322,41 @@ static int ovl_check_origin(struct dentry *upperdentry,
                return -ENOMEM;
        }
        **stackp = (struct ovl_path){.dentry = origin, .layer = lower[i].layer};
-       *ctrp = 1;
 
        return 0;
+
+invalid:
+       pr_warn_ratelimited("overlayfs: invalid origin (%pd2, ftype=%x, origin ftype=%x).\n",
+                           upperdentry, d_inode(upperdentry)->i_mode & S_IFMT,
+                           d_inode(origin)->i_mode & S_IFMT);
+       dput(origin);
+       return -EIO;
+}
+
+static int ovl_check_origin(struct dentry *upperdentry,
+                           struct ovl_path *lower, unsigned int numlower,
+                           struct ovl_path **stackp, unsigned int *ctrp)
+{
+       struct ovl_fh *fh = ovl_get_origin_fh(upperdentry);
+       int err;
+
+       if (IS_ERR_OR_NULL(fh))
+               return PTR_ERR(fh);
+
+       err = ovl_check_origin_fh(fh, upperdentry, lower, numlower, stackp);
+       kfree(fh);
+
+       if (err) {
+               if (err == -ESTALE)
+                       return 0;
+               return err;
+       }
+
+       if (WARN_ON(*ctrp))
+               return -EIO;
+
+       *ctrp = 1;
+       return 0;
 }
 
 /*
@@ -389,7 +430,6 @@ int ovl_verify_index(struct dentry *index, struct ovl_path *lower,
        size_t len;
        struct ovl_path origin = { };
        struct ovl_path *stack = &origin;
-       unsigned int ctr = 0;
        int err;
 
        if (!d_inode(index))
@@ -420,16 +460,18 @@ int ovl_verify_index(struct dentry *index, struct ovl_path *lower,
                goto fail;
 
        err = -EINVAL;
-       if (hex2bin((u8 *)fh, index->d_name.name, len) || len != fh->len)
+       if (hex2bin((u8 *)fh, index->d_name.name, len))
+               goto fail;
+
+       err = ovl_check_fh_len(fh, len);
+       if (err)
                goto fail;
 
        err = ovl_verify_origin_fh(index, fh);
        if (err)
                goto fail;
 
-       err = ovl_check_origin(index, lower, numlower, &stack, &ctr);
-       if (!err && !ctr)
-               err = -ESTALE;
+       err = ovl_check_origin_fh(fh, index, lower, numlower, &stack);
        if (err)
                goto fail;