From 147e88d88b5dfbcdd23aff736e4d381a8af446f6 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Tue, 20 Jan 2026 15:58:31 +0100 Subject: [PATCH] ovl: relax requirement for uuid=off,index=on uuid=off,index=on required that all upper/lower directories are on the same filesystem. Relax the requirement so that only all the lower directories need to be on the same filesystem. Signed-off-by: Amir Goldstein --- Documentation/filesystems/overlayfs.rst | 2 +- fs/overlayfs/namei.c | 21 +++++++++++++-------- fs/overlayfs/overlayfs.h | 2 ++ fs/overlayfs/super.c | 13 +++++-------- 4 files changed, 21 insertions(+), 17 deletions(-) diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst index ab989807a2cb6..d4020eae1deba 100644 --- a/Documentation/filesystems/overlayfs.rst +++ b/Documentation/filesystems/overlayfs.rst @@ -755,7 +755,7 @@ read-write mount and will result in an error. Note: the mount option uuid=off can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy -is changed. This is only applicable if all lower/upper/work directories are on +is changed. This is only applicable if all lower directories are on the same filesystem, otherwise it will fallback to normal behaviour. diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index e9a69c95be918..74c514603ac23 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -158,6 +158,18 @@ static struct ovl_fh *ovl_get_fh(struct ovl_fs *ofs, struct dentry *upperdentry, goto out; } +bool ovl_uuid_match(struct ovl_fs *ofs, const struct super_block *sb, + const uuid_t *uuid) +{ + /* + * Make sure that the stored uuid matches the uuid of the lower + * layer where file handle will be decoded. + * In case of uuid=off option just make sure that stored uuid is null. + */ + return ovl_origin_uuid(ofs) ? uuid_equal(uuid, &sb->s_uuid) : + uuid_is_null(uuid); +} + struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, struct vfsmount *mnt, bool connected) { @@ -167,14 +179,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, if (!capable(CAP_DAC_READ_SEARCH)) return NULL; - /* - * Make sure that the stored uuid matches the uuid of the lower - * layer where file handle will be decoded. - * In case of uuid=off option just make sure that stored uuid is null. - */ - if (ovl_origin_uuid(ofs) ? - !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid) : - !uuid_is_null(&fh->fb.uuid)) + if (!ovl_uuid_match(ofs, mnt->mnt_sb, &fh->fb.uuid)) return NULL; bytes = (fh->fb.len - offsetof(struct ovl_fb, fid)); diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index f9ac9bdde8305..cf10661522106 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -710,6 +710,8 @@ static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) return ovl_check_fb_len(&fh->fb, fh_len - OVL_FH_WIRE_OFFSET); } +bool ovl_uuid_match(struct ovl_fs *ofs, const struct super_block *sb, + const uuid_t *uuid); struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, struct vfsmount *mnt, bool connected); int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index ba9146f22a2cc..8f0ecb4905e93 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -940,7 +940,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) * disable lower file handle decoding on all of them. */ if (ofs->fs[i].is_lower && - uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) { + ovl_uuid_match(ofs, ofs->fs[i].sb, uuid)) { ofs->fs[i].bad_uuid = true; return false; } @@ -952,6 +952,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) { struct super_block *sb = path->mnt->mnt_sb; + const uuid_t *uuid = ovl_origin_uuid(ofs) ? &sb->s_uuid : &uuid_null; unsigned int i; dev_t dev; int err; @@ -963,7 +964,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) return i; } - if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { + if (!ovl_lower_uuid_ok(ofs, uuid)) { bad_uuid = true; if (ofs->config.xino == OVL_XINO_AUTO) { ofs->config.xino = OVL_XINO_OFF; @@ -976,8 +977,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) } if (warn) { pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n", - uuid_is_null(&sb->s_uuid) ? "null" : - "conflicting", + uuid_is_null(uuid) ? "null" : "conflicting", path->dentry, ovl_xino_mode(&ofs->config)); } } @@ -1469,10 +1469,7 @@ static int ovl_fill_super_creds(struct fs_context *fc, struct super_block *sb) if (!ovl_upper_mnt(ofs)) sb->s_flags |= SB_RDONLY; - if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) { - pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n"); - ofs->config.uuid = OVL_UUID_NULL; - } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) { + if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) { /* Use per instance persistent uuid/fsid */ ovl_init_uuid_xattr(sb, ofs, &ctx->upper); } -- 2.52.0