From beae836e9c61ee039e367a94b14f7fea08f0ad4c Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Sat, 14 Oct 2023 22:30:04 +0300 Subject: [PATCH] ovl: temporarily disable appending lowedirs Kernel v6.5 converted overlayfs to new mount api. As an added bonus, it also added a feature to allow appending lowerdirs using lowerdir=:/lower2,lowerdir=::/data3 syntax. This new syntax has raised some concerns regarding escaping of colons. We decided to try and disable this syntax, which hasn't been in the wild for so long and introduce it again in 6.7 using explicit mount options lowerdir+=/lower2,datadir+=/data3. Suggested-by: Miklos Szeredi Link: https://lore.kernel.org/r/CAJfpegsr3A4YgF2YBevWa6n3=AcP7hNndG6EPMu3ncvV-AM71A@mail.gmail.com/ Fixes: b36a5780cb44 ("ovl: modify layer parameter parsing") Signed-off-by: Amir Goldstein --- fs/overlayfs/params.c | 52 +++---------------------------------------- 1 file changed, 3 insertions(+), 49 deletions(-) diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c index 8b6bae320e8a26..f6ff23fd101c8f 100644 --- a/fs/overlayfs/params.c +++ b/fs/overlayfs/params.c @@ -350,12 +350,6 @@ static void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx) * Set "/lower1", "/lower2", and "/lower3" as lower layers and * "/data1" and "/data2" as data lower layers. Any existing lower * layers are replaced. - * (2) lowerdir=:/lower4 - * Append "/lower4" to current stack of lower layers. This requires - * that there already is at least one lower layer configured. - * (3) lowerdir=::/lower5 - * Append data "/lower5" as data lower layer. This requires that - * there's at least one regular lower layer present. */ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc) { @@ -377,49 +371,9 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc) return 0; } - if (strncmp(name, "::", 2) == 0) { - /* - * This is a data layer. - * There must be at least one regular lower layer - * specified. - */ - if (ctx->nr == 0) { - pr_err("data lower layers without regular lower layers not allowed"); - return -EINVAL; - } - - /* Skip the leading "::". */ - name += 2; - data_layer = true; - /* - * A data layer is automatically an append as there - * must've been at least one regular lower layer. - */ - append = true; - } else if (*name == ':') { - /* - * This is a regular lower layer. - * If users want to append a layer enforce that they - * have already specified a first layer before. It's - * better to be strict. - */ - if (ctx->nr == 0) { - pr_err("cannot append layer if no previous layer has been specified"); - return -EINVAL; - } - - /* - * Once a sequence of data layers has started regular - * lower layers are forbidden. - */ - if (ctx->nr_data > 0) { - pr_err("regular lower layers cannot follow data lower layers"); - return -EINVAL; - } - - /* Skip the leading ":". */ - name++; - append = true; + if (*name == ':') { + pr_err("cannot append lower layer"); + return -EINVAL; } dup = kstrdup(name, GFP_KERNEL);