ovl: lookup non-dir copy-up-origin by file handle (a9d01957) · Commits · 戴 / test

fs/overlayfs/namei.c

+132 −0

Original line number	Diff line number	Diff line
		@@ -12,6 +12,8 @@
		#include <linux/namei.h>
		#include <linux/xattr.h>
		#include <linux/ratelimit.h>
		#include <linux/mount.h>
		#include <linux/exportfs.h>
		#include "overlayfs.h"
		#include "ovl_entry.h"

		@@ -81,6 +83,90 @@ invalid:
		goto err_free;
		}

		static int ovl_acceptable(void ctx, struct dentry dentry)
		{
		return 1;
		}

		static struct dentry ovl_get_origin(struct dentry dentry,
		struct vfsmount *mnt)
		{
		int res;
		struct ovl_fh *fh = NULL;
		struct dentry *origin = NULL;
		int bytes;

		res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
		if (res < 0) {
		if (res == -ENODATA \|\| res == -EOPNOTSUPP)
		return NULL;
		goto fail;
		}
		/* Zero size value means "copied up but origin unknown" */
		if (res == 0)
		return NULL;

		fh = kzalloc(res, GFP_TEMPORARY);
		if (!fh)
		return ERR_PTR(-ENOMEM);

		res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, fh, res);
		if (res < 0)
		goto fail;

		if (res < sizeof(struct ovl_fh) \|\| res < fh->len)
		goto invalid;

		if (fh->magic != OVL_FH_MAGIC)
		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;

		bytes = (fh->len - offsetof(struct ovl_fh, fid));

		/*
		* Make sure that the stored uuid matches the uuid of the lower
		* layer where file handle will be decoded.
		*/
		if (uuid_be_cmp(fh->uuid, (uuid_be ) &mnt->mnt_sb->s_uuid))
		goto out;

		origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
		bytes >> 2, (int)fh->type,
		ovl_acceptable, NULL);
		if (IS_ERR(origin)) {
		/* Treat stale file handle as "origin unknown" */
		if (origin == ERR_PTR(-ESTALE))
		origin = NULL;
		goto out;
		}

		if (ovl_dentry_weird(origin) \|\|
		((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT)) {
		dput(origin);
		origin = NULL;
		goto invalid;
		}

		out:
		kfree(fh);
		return origin;

		fail:
		pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);
		goto out;
		invalid:
		pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);
		goto out;
		}

		static bool ovl_is_opaquedir(struct dentry *dentry)
		{
		int res;
		@@ -192,6 +278,45 @@ static int ovl_lookup_layer(struct dentry base, struct ovl_lookup_data d,
		return 0;
		}


		static int ovl_check_origin(struct dentry dentry, struct dentry upperdentry,
		struct path *stackp, unsigned int ctrp)
		{
		struct super_block *same_sb = ovl_same_sb(dentry->d_sb);
		struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
		struct vfsmount *mnt;
		struct dentry *origin;

		if (!same_sb \|\| !roe->numlower)
		return 0;

		/*
		* Since all layers are on the same fs, we use the first layer for
		* decoding the file handle. We may get a disconnected dentry,
		* which is fine, because we only need to hold the origin inode in
		* cache and use its inode number. We may even get a connected dentry,
		* that is not under the first layer's root. That is also fine for
		* using it's inode number - it's the same as if we held a reference
		* to a dentry in first layer that was moved under us.
		*/
		mnt = roe->lowerstack[0].mnt;

		origin = ovl_get_origin(upperdentry, mnt);
		if (IS_ERR_OR_NULL(origin))
		return PTR_ERR(origin);

		BUG_ON(stackp \|\| ctrp);
		*stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
		if (!*stackp) {
		dput(origin);
		return -ENOMEM;
		}
		**stackp = (struct path) { .dentry = origin, .mnt = mnt };
		*ctrp = 1;

		return 0;
		}

		/*
		* Returns next layer in stack starting from top.
		* Returns -1 if this is the last layer.
		@@ -254,6 +379,13 @@ struct dentry ovl_lookup(struct inode dir, struct dentry *dentry,
		err = -EREMOTE;
		goto out;
		}
		if (upperdentry && !d.is_dir) {
		BUG_ON(!d.stop \|\| d.redirect);
		err = ovl_check_origin(dentry, upperdentry,
		&stack, &ctr);
		if (err)
		goto out;
		}

		if (d.redirect) {
		upperredirect = kstrdup(d.redirect, GFP_KERNEL);

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