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=1794411640; b=AMzMPVxmUObprPv0Vpsg7dvRxqpEaasUDqgknlf0eE2RLkaLTJpzWNis6yiKZfXSYRDa kUwcrKdv3lTqjxelZY76dYpK0tt8GomMQt2BSIWiyKNBBXLRot+mAUda5YpMJW1kxTKia 0Pzc/yJGaYyQ311ebeCRMhjeh0QFMkYVpSzJI4M4FJldq1Drrv6pBHAgNrg9TFvUZ8Rwx 7JzTALzvvGJPM0jtc57WfIAoOekzBoKva26EoAhMAV8KQBjmrGspnDx7YbR3/5QajgoZJ y8a+uoOYlS2WWIRGNTuVION+5smefZfz5PUa1l8XdUBNcBPhyooOp+W1RDbYS/C6g0w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794411640; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=7psbhEe83ARPQGQMdJuc9eUmH52qRk1QiQuWpxhrKQ8=; b=TYtfTdYffTObiDvflVREulN9gwNdS10VRTHuYLXfgsxAAD3tmAbmCeh+ytpjPOZwSEUj zdAg3q8O/i+RtXmFAIs4OoCsVnw+zQ40Ts4+bBuoHQOwwf5ijRA/ILFHoAK7omMBsYe62 OKPpPuFkSIfwMNIXMH5oJM/uV6dE176dIHRZGkROdocq1vU/JBqvSo7eZDiuSNAnEspOa mD3EkJXI/PwcKhII38x5si+WteCOZxzh9fZXxdSjSGD/lJBw/VETd9GIPWG9+vogiw6BD /IfkxoYkhQyEH3qmz3NFNpGSllFhkUiD9oR4H3hIl0BHtmv394V7bqN2V3pQgNJZD5w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XuX3KTRj; 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 1E21C606A324 for ; Wed, 11 Nov 2026 15:40:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XuX3KTRj Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A9DE1F00A07; Wed, 11 Nov 2026 15:40:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794411639; bh=7psbhEe83ARPQGQMdJuc9eUmH52qRk1QiQuWpxhrKQ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XuX3KTRjKdti7b+gKKWJ6bvOpBj5V8IocD1ZfJhojTW0FcSF88XagrP9CGXIi4awZ nhixJ6u3VywO9m5LeWhfxEKYEYrDODFeujHVBphJ0jjuzNYsDpRckj/Ekb5Tj4NUdO mZkPLcdS1ujQKBLI8n/rrHc+0TPTKwD60lcRnV3QAstKJ1Tty5qjJq0CF1Fbouh1gQ 8b5tjPBc8SaGIU1bdSyanaZ5kRS/GfMJGmsErwJRaTi9fa0deTIT/dzD0JvOHwAhGs o2/SsDD/8KkmfdBtGfoJ6vDJ4ss951JdtzX3qs5sOXQT0TxjmfNfZJyVncSwrZu2Fy 05KPPucagtnzQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Daehyeon Ko <4ncienth@gmail.com>, "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.1.y 3/3] splice: avoid stale f_pos writeback on error Date: Wed, 11 Nov 2026 10:40:36 -0500 Message-ID: <20261111154025.2714356-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261111154025.2714356-1-sashal@kernel.org> References: <20261107055657-failed-6.1-79b496ebe382@kernel.org> <20261111154025.2714356-1-sashal@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Daehyeon Ko <4ncienth@gmail.com> [ Upstream commit 79b496ebe382866e3a05090b7dc9ae95e85e65b2 ] do_splice() snapshots an implicit file position before calling the splice helper. Since splice does not take f_pos_lock, another operation on the same open file description can update f_pos while the helper is blocked. If the helper then fails, the unconditional writeback restores the stale snapshot. For a directory without ->splice_read, a file-to-pipe splice fails with -EINVAL. A concurrent directory mutation and getdents() call can advance f_pos and refresh the filesystem's revalidation cookie before that failure restores only the old position. The next ext2 readdir can then trust an offset inside a directory entry and copy data from the adjacent page to userspace. Only update an implicit file position when splice returns a non-negative result, matching read and write. Keep explicit offset updates unchanged. Fixes: 7995bd287134 ("splice: don't pass the address of ->f_pos to methods") Cc: stable@vger.kernel.org Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> Link: https://patch.msgid.link/20261018051708.2422394-1-4ncienth@gmail.com Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Sasha Levin --- fs/splice.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index ea92caf95a385..418c03d9b9f84 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1101,10 +1101,10 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out, ret = do_splice_from(ipipe, out, &offset, len, flags); file_end_write(out); - if (!off_out) - out->f_pos = offset; - else + if (off_out) *off_out = offset; + else if (ret >= 0) + out->f_pos = offset; } else if (opipe) { if (off_out) return -ESPIPE; @@ -1121,10 +1121,10 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out, ret = splice_file_to_pipe(in, opipe, &offset, len, flags); - if (!off_in) - in->f_pos = offset; - else + if (off_in) *off_in = offset; + else if (ret >= 0) + in->f_pos = offset; } else { ret = -EINVAL; } -- 2.53.0