From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793831598; b=jq5emxpCApGEYISYU2JIk1jz8z0EaB3Klk2bAhdStxdHqvVnOTDl4E6+du5dIZLqdcrL sTKwjXZDgx/G5QotRcmSfl7E836LZZWbrklLhYCkYPyLLVFOJ6+s1F5GHlJ/smdGtAGJT 09daGHNwyQSnBxo1RY1/fv0S085ZBrmF7w5254dbuf6Vt5SMYMN92vr/qrTdhtkP6qD1l zxDIq50r//9QVx0+dwv0/0hCyc6oLy6bFACMUaRGjSnEfzj7y+Cx+UUe+/U5bvn0feMsQ wzXOs3FC7XsGUQcnertUv6X2rkPaqG73mCmMVBREd3lC+e/CTEolpKtxhlYk3/Krvzg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831598; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=Xhvu35COQSHvGOTd9wtuD9yUFNm0nnDbn1TQJP4zNCQ=; b=t38XoIvDZigPRPTsMAc3sxNCXOHsWb62EIduFR6wr/Z++Ce/Nt5l3Q42M1F6F2m8sFeW GUZvGlGupvdDyeS1kAoC3dfVIJEeygkJ4J1IORkvspERC/ZzGch2cpWVkfZR4ABo2x7yq kwtyqKP52L6sfWq38dgYU8XvkjrKrU66nc5vbyi5v2Wwse1d43f6qfAnfB0Won6noM0xb HrdFQ5X9a5vTIUn90VwwRZjKhMVKTibs//QPoSX/rqQwtFv5DZ1WSsL685e2WHG81N7i7 +4nG1YPHIBHVzBulD9rYabEL+/nSOCwK3q12rvCOhjwtPnzrnc/K5xgAfmGexwZDkwA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=OfzXcaDv; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3652606A844; Wed, 4 Nov 2026 22:33:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=OfzXcaDv Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7EF141F00A02; Wed, 4 Nov 2026 22:33:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831597; bh=Xhvu35COQSHvGOTd9wtuD9yUFNm0nnDbn1TQJP4zNCQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=OfzXcaDvlsSC/w0QRtvqUTbE91Tp680zkpx0Iv+zwUirEvR/y3Ie4RJfNB48vGTXl MZF9NlMm3gU2jew8KBMpMSUnXQ2oHt9+2kgEmyh/0E9LdCBEc6xgUgfiBiV2Ar6Lvd vzSIPX+Ip2PyDFOuYR02yUyc5kMH/93OXBTfWmY0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Josef Bacik , Amir Goldstein Subject: [PATCH 6.18 0762/1005] ovl: take a snapshot of the name for copy up Date: Wed, 4 Nov 2026 16:08:15 -0500 Message-ID: <20261104211104.766349833@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason commit 65bf000962a33ec9d2488e4e1797b6cf630abcbb upstream. The copy up of a directory reads a freed dentry name when a lookup moves the directory at the same time. A pointer to the name of a dentry is only valid while something stops a move of the dentry. ovl_do_copy_up() keeps a plain copy of c->dentry->d_name in c->destname, and ovl_copy_up_start() only keeps ovl_rename() away. When a lookup finds the same directory under another name after a change to the lower layer, d_splice_alias() moves the dentry and frees its external name. With a delay in ovl_do_copy_up(), a chmod of a lower-only directory with a 60 byte name raced with a rename of that directory in the lower layer and a stat of the new name, and KASAN reported a use-after-free in lookup_noperm_common(). Fix this by using take_dentry_name_snapshot() for c->destname. Fixes: 829c28be9bb9 ("ovl: use d_splice_alias() in place of d_add() in lookup") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Signed-off-by: Josef Bacik Signed-off-by: Amir Goldstein Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/copy_up.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -948,6 +948,7 @@ static int ovl_do_copy_up(struct ovl_cop struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb); struct dentry *origin = c->lowerpath.dentry; struct ovl_fh *fh = NULL; + struct name_snapshot name; bool to_index = false; /* @@ -985,12 +986,15 @@ static int ovl_do_copy_up(struct ovl_cop goto out_free_fh; } else { /* - * c->dentry->d_name is stabilzed by ovl_copy_up_start(), - * because if we got here, it means that c->dentry has no upper - * alias and changing ->d_name means going through ovl_rename() - * that will call ovl_copy_up() on source and target dentry. + * ovl_copy_up_start() keeps ovl_rename() away from c->dentry, + * because ovl_rename() calls ovl_copy_up() on source and target + * dentry. It does not stop d_splice_alias() from moving a + * directory that a lookup found under another name after a + * change to the lower layer. That move frees an external name, + * so take a snapshot. */ - c->destname = c->dentry->d_name; + take_dentry_name_snapshot(&name, c->dentry); + c->destname = name.name; /* * Mark parent "impure" because it may now contain non-pure * upper @@ -999,7 +1003,7 @@ static int ovl_do_copy_up(struct ovl_cop err = ovl_set_impure(c->parent, c->destdir); ovl_end_write(c->dentry); if (err) - goto out_free_fh; + goto out; } /* Should we copyup with O_TMPFILE or with workdir? */ @@ -1033,6 +1037,8 @@ static int ovl_do_copy_up(struct ovl_cop out: if (to_index) kfree(c->destname.name); + else + release_dentry_name_snapshot(&name); out_free_fh: kfree(fh); return err;