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ovl: fix corner case of non-constant st_dev;st_ino

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On non-samefs overlay without xino, non pure upper inodes should use a
pseudo_dev assigned to each unique lower fs, but if lower layer is on the
same fs and upper layer, it has no pseudo_dev assigned.

In this overlay layers setup:
 - two filesystems, A and B
 - upper layer is on A
 - lower layer 1 is also on A
 - lower layer 2 is on B

Non pure upper overlay inode, whose origin is in layer 1 will have the
st_dev;st_ino values of the real lower inode before copy up and the
st_dev;st_ino values of the real upper inode after copy up.

Fix this inconsitency by assigning a unique pseudo_dev also for upper fs,
that will be used as st_dev value along with the lower inode st_dev for
overlay inodes in the case above.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein 2020-01-14 22:17:25 +02:00 committed by Miklos Szeredi
parent 1b81dddd35
commit b7bf9908e1
2 changed files with 14 additions and 17 deletions
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16
fs/overlayfs/inode.c
View File

@ -121,13 +121,12 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
*/
stat->dev = dentry->d_sb->s_dev;
stat->ino = dentry->d_inode->i_ino;
} else if (fsid) {
} else {
/*
* For non-samefs setup, if we cannot map all layers st_ino
* to a unified address space, we need to make sure that st_dev
* is unique per lower fs. Upper layer uses real st_dev and
* lower layers use the unique anonymous bdev assigned to the
* lower fs.
* is unique per underlying fs, so we use the unique anonymous
* bdev assigned to the underlying fs.
*/
stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;
}
@ -143,7 +142,6 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
struct path realpath;
const struct cred *old_cred;
bool is_dir = S_ISDIR(dentry->d_inode->i_mode);
bool samefs = ovl_same_fs(dentry->d_sb);
int fsid = 0;
int err;
bool metacopy_blocks = false;
@ -198,13 +196,7 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
(!ovl_verify_lower(dentry->d_sb) &&
(is_dir || lowerstat.nlink == 1))) {
fsid = ovl_layer_lower(dentry)->fsid;
/*
* Cannot use origin st_dev;st_ino because
* origin inode content may differ from overlay
* inode content.
*/
if (samefs || fsid)
stat->ino = lowerstat.ino;
stat->ino = lowerstat.ino;
}
/*

15
fs/overlayfs/super.c
View File

@ -229,8 +229,7 @@ static void ovl_free_fs(struct ovl_fs *ofs)
mntput(ofs->layers[i].mnt);
}
kfree(ofs->layers);
/* fs[0].pseudo_dev is either null or real upper st_dev */
for (i = 1; i < ofs->numfs; i++)
for (i = 0; i < ofs->numfs; i++)
free_anon_bdev(ofs->fs[i].pseudo_dev);
kfree(ofs->fs);
@ -1341,13 +1340,19 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
ofs->numlayer = 1;
/*
* All lower layers that share the same fs as upper layer, use the real
* upper st_dev.
* All lower layers that share the same fs as upper layer, use the same
* pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
* only overlay to simplify ovl_fs_free().
* is_lower will be set if upper fs is shared with a lower layer.
*/
err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
if (err) {
pr_err("failed to get anonymous bdev for upper fs\n");
goto out;
}
if (ofs->upper_mnt) {
ofs->fs[0].sb = ofs->upper_mnt->mnt_sb;
ofs->fs[0].pseudo_dev = ofs->upper_mnt->mnt_sb->s_dev;
ofs->fs[0].is_lower = false;
}