From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 047B9252910 for ; Wed, 4 Jun 2025 11:57:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749038235; cv=none; b=WZbOJcRDVKxtST5XFZKGTFpQwLA6fmRuRqZH40WTvpEpmgdYeayqwnlChtE/D+G/0ARV9oLzpQL2f0a6WW3fLK56uYBErRvVy59k3PPWU7bQ6azjRpSpkU8zWk0u05kSUC/xUKLDbEg0uBQRWr3tcZu8LZprpYVIZ61JbHeMrgI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749038235; c=relaxed/simple; bh=TaU8NXrxQxAJmhut88PXxzpUUiiPrXmm64aa+eogRPM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=gGHO6CK8H6sA79+fipRfnt3lagkX3T1cUYTfOC9WHDTaE9Ku1uKI3MxGqm0vc6Cs1XMqD0cnoM188ZaqcCPPk8m8VUoow6+GJQisVBqaqEEYySmoU1mZ7NtHkaE8GDkK2rbOwmgM1E20o3qygQMHr1slDQhnTWH0fHPNWeA+AX8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kvxCcCLp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kvxCcCLp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EED25C4CEE7; Wed, 4 Jun 2025 11:57:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749038234; bh=TaU8NXrxQxAJmhut88PXxzpUUiiPrXmm64aa+eogRPM=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=kvxCcCLppvHSUw6iAlv9PRpQleuZUGGf1PnvcYckp2zB7vz9Gv6C91vPxZvZoLdNf 8aUcxUOZqC5YZFPP+gBY/uGTuNHTfybrNRQl2uSCwf4guc+KcOMgi5SEGCEC3kzlI+ pbNDMu1xjPzsCMAeUcV/dZDAB2XOemSp4petJCBthem0TONfO80EeXSBRVLQnCEaEz rGL6aKQARDp1k209wPolzo7KaC6xR6h0aeC1NS/67raXKF17YMsiGoTcsb5vGx6vKj 49PJacX/8jrkEX7fCZq4mRBD6gQbfwo74jCIknUfh0AZfLEGI9pX4odPWLA4QLOi/C GsKZzoVtyTCYg== Message-ID: Subject: Re: [PATCH 1/5] fs/fhandle.c: fix a race in call of has_locked_children() From: Jeff Layton To: Al Viro , linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Christian Brauner , Jan Kara , Amir Goldstein Date: Wed, 04 Jun 2025 07:57:13 -0400 In-Reply-To: <20250603231632.GA145532@ZenIV> References: <20250603231500.GC299672@ZenIV> <20250603231632.GA145532@ZenIV> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV 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> The rest of the callers are safe since they are holding namespace_sem and > are guaranteed a positive refcount on the mount in question. >=20 > Rename the current has_locked_children() to __has_locked_children(), make > it static and switch the fs/namespace.c users to it. >=20 > Make has_locked_children() a wrapper for __has_locked_children(), calling > the latter under read_seqlock_excl(&mount_lock). >=20 > Fixes: 620c266f3949 ("fhandle: relax open_by_handle_at() permission check= s") > Signed-off-by: Al Viro > --- > fs/namespace.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) >=20 > diff --git a/fs/namespace.c b/fs/namespace.c > index 7c0ebc4f4ef2..a33553bc12d0 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -2425,7 +2425,7 @@ void drop_collected_mounts(struct vfsmount *mnt) > namespace_unlock(); > } > =20 > -bool has_locked_children(struct mount *mnt, struct dentry *dentry) > +static bool __has_locked_children(struct mount *mnt, struct dentry *dent= ry) > { > struct mount *child; > =20 > @@ -2439,6 +2439,16 @@ bool has_locked_children(struct mount *mnt, struct= dentry *dentry) > return false; > } > =20 > +bool has_locked_children(struct mount *mnt, struct dentry *dentry) > +{ > + bool res; > + > + read_seqlock_excl(&mount_lock); > + res =3D __has_locked_children(mnt, dentry); > + read_sequnlock_excl(&mount_lock); > + return res; > +} > + > /* > * Check that there aren't references to earlier/same mount namespaces i= n the > * specified subtree. Such references can act as pins for mount namespa= ces > @@ -2499,7 +2509,7 @@ struct vfsmount *clone_private_mount(const struct p= ath *path) > return ERR_PTR(-EINVAL); > } > =20 > - if (has_locked_children(old_mnt, path->dentry)) > + if (__has_locked_children(old_mnt, path->dentry)) > return ERR_PTR(-EINVAL); > =20 > new_mnt =3D clone_mnt(old_mnt, path->dentry, CL_PRIVATE); > @@ -3036,7 +3046,7 @@ static struct mount *__do_loopback(struct path *old= _path, int recurse) > if (!may_copy_tree(old_path)) > return mnt; > =20 > - if (!recurse && has_locked_children(old, old_path->dentry)) > + if (!recurse && __has_locked_children(old, old_path->dentry)) > return mnt; > =20 > if (recurse) > @@ -3429,7 +3439,7 @@ static int do_set_group(struct path *from_path, str= uct path *to_path) > goto out; > =20 > /* From mount should not have locked children in place of To's root */ > - if (has_locked_children(from, to->mnt.mnt_root)) > + if (__has_locked_children(from, to->mnt.mnt_root)) > goto out; > =20 > /* Setting sharing groups is only allowed on private mounts */ Good catch! Reviewed-by: Jeff Layton