On Fri, May 23, 2025 at 7:14 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > On Fri, May 23, 2025 at 4:10 PM Kent Overstreet > <kent.overstreet@xxxxxxxxx> wrote: > > > > On Tue, May 20, 2025 at 04:33:14PM +0200, Amir Goldstein wrote: > > > I am saying that IMO a smaller impact (and less user friendly) fix is more > > > appropriate way to deal with this problem. > > > > What do you think about doing your approach as a stopgap? > > > > It seems this is hitting a lot of people, something we can backport to > > 6.15 would be good to have. > > Yes, I think I can do that. > Will try to get to it next week. > On second look, here is a compile-basic-sanity-tested patch. Care to test if it does the job for you? Thanks, Amir.
From 9fd9ce0e2b6de84b3665ed743b36348006739cd3 Mon Sep 17 00:00:00 2001 From: Amir Goldstein <amir73il@xxxxxxxxx> Date: Fri, 23 May 2025 22:13:18 +0200 Subject: [PATCH] ovl: support casefolded filesystems Case folding is often applied to subtrees and not on an entire filesystem. Disallowing layers from filesystems that support case folding is over limiting. Replace the rule that case-folding capable are not allowed as layers with a rule that case folded directories are not allowed in a merged directory stack. Should case folding be enabled on an underlying directory while overlayfs is mounted the outcome is generally undefined. Specifically in ovl_lookup(), we check the base underlying directory and fail with -ESTALE if an underlying directory case folding is enabled. Suggested-by: Kent Overstreet <kent.overstreet@xxxxxxxxx> Link: https://lore.kernel.org/linux-fsdevel/20250520051600.1903319-1-kent.overstreet@xxxxxxxxx/ Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- fs/overlayfs/namei.c | 10 ++++++++++ fs/overlayfs/params.c | 10 ++++------ fs/overlayfs/util.c | 15 +++++++++++---- 3 files changed, 25 insertions(+), 10 deletions(-) diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index d489e80feb6f..5168b72d9710 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -237,6 +237,16 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d, bool is_upper = d->layer->idx == 0; char val; + /* + * We allow filesystems that are case-folding capable but deny composing + * ovl stack from case-folded directories. If someone has enabled case + * folding on a directory on underlying layer, the warranty of the ovl + * stack is voided. + */ + err = -ESTALE; + if (sb_has_encoding(base->d_sb) && IS_CASEFOLDED(d_inode(base))) + goto out; + this = ovl_lookup_positive_unlocked(d, name, base, namelen, drop_negative); if (IS_ERR(this)) { err = PTR_ERR(this); diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c index f42488c01957..30cd7145b234 100644 --- a/fs/overlayfs/params.c +++ b/fs/overlayfs/params.c @@ -282,13 +282,11 @@ static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path, return invalfc(fc, "%s is not a directory", name); /* - * Root dentries of case-insensitive capable filesystems might - * not have the dentry operations set, but still be incompatible - * with overlayfs. Check explicitly to prevent post-mount - * failures. + * Allow filesystems that are case-folding capable but deny composing + * ovl stack from case-folded directories. */ - if (sb_has_encoding(path->mnt->mnt_sb)) - return invalfc(fc, "case-insensitive capable filesystem on %s not supported", name); + if (sb_has_encoding(path->mnt->mnt_sb) && IS_CASEFOLDED(d_inode(path->dentry))) + return invalfc(fc, "case-insensitive directory on %s not supported", name); if (ovl_dentry_weird(path->dentry)) return invalfc(fc, "filesystem on %s not supported", name); diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index dcccb4b4a66c..593c4da107d6 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -206,10 +206,17 @@ bool ovl_dentry_weird(struct dentry *dentry) if (!d_can_lookup(dentry) && !d_is_file(dentry) && !d_is_symlink(dentry)) return true; - return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT | - DCACHE_MANAGE_TRANSIT | - DCACHE_OP_HASH | - DCACHE_OP_COMPARE); + if (dentry->d_flags & (DCACHE_NEED_AUTOMOUNT | DCACHE_MANAGE_TRANSIT)) + return true; + + /* + * Allow filesystems that are case-folding capable but deny composing + * ovl stack from case-folded directories. + */ + if (sb_has_encoding(dentry->d_sb)) + return IS_CASEFOLDED(d_inode(dentry)); + + return dentry->d_flags & (DCACHE_OP_HASH | DCACHE_OP_COMPARE); } enum ovl_path_type ovl_path_type(struct dentry *dentry) -- 2.34.1
