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ovl: use is_subdir() for testing if one thing is a subdir of another

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Rather than using lock_rename(), use the more obvious is_subdir() for
ensuring that neither upper nor workdir contain the other.
Also be explicit in the comment that the two directories cannot be the
same.

As this is a point-it-time sanity check and does not provide any
on-going guarantees, the removal of locking does not introduce any
interesting races.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20260224222542.3458677-14-neilb@ownmail.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
NeilBrown
2026-02-25 09:16:58 +11:00
committed by Christian Brauner
parent 8348278650
commit 56c8fd738e
1 changed files with 5 additions and 10 deletions
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15
fs/overlayfs/super.c
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@@ -451,18 +451,13 @@ static int ovl_lower_dir(const char *name, const struct path *path,
return 0;
}
/* Workdir should not be subdir of upperdir and vice versa */
/*
* Workdir should not be subdir of upperdir and vice versa, and
* they should not be the same.
*/
static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
{
bool ok = false;
if (workdir != upperdir) {
struct dentry *trap = lock_rename(workdir, upperdir);
if (!IS_ERR(trap))
unlock_rename(workdir, upperdir);
ok = (trap == NULL);
}
return ok;
return !is_subdir(workdir, upperdir) && !is_subdir(upperdir, workdir);
}
static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,