From 1f7168b28f667c0920fd83151ae35ce593950663 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Andr=C3=A9=20Almeida?= Date: Thu, 14 Aug 2025 14:22:16 -0300 Subject: [PATCH] ovl: Ensure that all layers have the same encoding MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When merging layers from different filesystems with casefold enabled, all layers should use the same encoding version and have the same flags to avoid any kind of incompatibility issues. Also, set the encoding and the encoding flags for the ovl super block as the same as used by the first valid layer. Reviewed-by: Amir Goldstein Signed-off-by: André Almeida Signed-off-by: Amir Goldstein --- fs/overlayfs/super.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index df85a76597e91..548ea9b1a48d4 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -991,6 +991,25 @@ static int ovl_get_data_fsid(struct ovl_fs *ofs) return ofs->numfs; } +/* + * Set the ovl sb encoding as the same one used by the first layer + */ +static int ovl_set_encoding(struct super_block *sb, struct super_block *fs_sb) +{ + if (!sb_has_encoding(fs_sb)) + return 0; + +#if IS_ENABLED(CONFIG_UNICODE) + if (sb_has_strict_encoding(fs_sb)) { + pr_err("strict encoding not supported\n"); + return -EINVAL; + } + + sb->s_encoding = fs_sb->s_encoding; + sb->s_encoding_flags = fs_sb->s_encoding_flags; +#endif + return 0; +} static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, struct ovl_fs_context *ctx, struct ovl_layer *layers) @@ -1024,6 +1043,12 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, if (ovl_upper_mnt(ofs)) { ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb; ofs->fs[0].is_lower = false; + + if (ofs->casefold) { + err = ovl_set_encoding(sb, ofs->fs[0].sb); + if (err) + return err; + } } nr_merged_lower = ctx->nr - ctx->nr_data; @@ -1083,6 +1108,19 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, l->name = NULL; ofs->numlayer++; ofs->fs[fsid].is_lower = true; + + if (ofs->casefold) { + if (!ovl_upper_mnt(ofs) && !sb_has_encoding(sb)) { + err = ovl_set_encoding(sb, ofs->fs[fsid].sb); + if (err) + return err; + } + + if (!sb_same_encoding(sb, mnt->mnt_sb)) { + pr_err("all layers must have the same encoding\n"); + return -EINVAL; + } + } } /* -- 2.47.3