From: Amir Goldstein amir73il@gmail.com
mainline inclusion from mainline-5.6-rc1 commit b7bf9908e17c4dc4b80876f299ac03ddf188efd9 category: bugfix bugzilla: 37632 CVE: NA
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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 Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/overlayfs/inode.c | 16 ++++------------ fs/overlayfs/super.c | 15 ++++++++++----- 2 files changed, 14 insertions(+), 17 deletions(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index b20202de78fd..252a3c6b4744 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -124,13 +124,12 @@ 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; } @@ -146,7 +145,6 @@ 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; @@ -201,13 +199,7 @@ 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; }
/* diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 256984859e53..48bb2f4ee05e 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -234,8 +234,7 @@ 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);
@@ -1344,13 +1343,19 @@ 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; }