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=1794063770; b=nHYcsQokqcb9XCRhK1FPY57DMHa328rLTsmM3KSBqa+3BHCPwZnZm2yc14cHGOJ68sqb s54/WDrVqfBZnRktXiDiEbJh++EIYINQV+ZLXJcFZk6r6+Jr7DE+zrsHo6IxJQembfxyu dDzDzUguzw8WyVrkEXrXmpMeOU90bXt6qsGpWhjKOe/tfbPVO6mxJ1qOtWXbfrHNSU/CA EjpbhndcYvwfcAo2vhPphXByQHarJphez4cjXqva1lHBUksCalJuo6igD7nqV++43bTiR hjMbtqiUXwqEkvQ6kBSooKlcEruP7vy+ncnnN0lw/I3+ZggV9jmSb+hIXy/Y0rwySaQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063770; 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=29dvBlNx4H/lerupypcKdG3quCT9uKKusC71fR/FO5A=; b=B1kB5o9Og1jADakxJO29FUV6hW201DufsRpJJo7gym2jRcPwfOMC8HST6ojeb6OQeUm+ jFNCWKFAOJgA7aQiBFjmxnc3PegLubSJ6BVY1QfTXSLNG34BQ+HUNRIynYaM+N4iIElxy 9lNUl3YCOeDZwV2FzHhyxPG9fKVXD0OnPVpWKDAehnNrhLdEqMfINPdlEq8EJVSlbvJeG HpoeoE6gRJ+GY3RQ2VCzfQN5ymuYUYI5128VntzLmSTMjZesZ8XjfG745ikVO2hAUuyKN nNHsHJgPA5ut+GCyojCrSUA2FblL/HgDUDRHE3eQi4JrThn3xeF+iXidAACk547kOvA== 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=AdBDZYZE; 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 76E4F60A261D; Sat, 7 Nov 2026 15:02:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=AdBDZYZE Received: by smtp.kernel.org (Postfix) with ESMTPSA id 256121F0089F; Sat, 7 Nov 2026 15:02:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063770; bh=29dvBlNx4H/lerupypcKdG3quCT9uKKusC71fR/FO5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=AdBDZYZEUJDN2ymQ6BLNWOaZBfN2M3odcjtgjXtmbJsPlIGcRkS0yO0wFyySh5x+N ewUks5PM4hm6fj7UI0yDf9SEWotcZZuelYuwNdDXGDmt4U3EcMOw8NcAqD0fYEnpzD WGScxnBvAuZ21hbh1ad76QJVrZmtiJ/ZWjfzfz9c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Daehyeon Ko <4ncienth@gmail.com>, "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.18 862/869] splice: avoid stale f_pos writeback on error Date: Sat, 7 Nov 2026 08:59:04 -0500 Message-ID: <20261107134922.046322380@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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 f5094b6d00a09..8ac45441e2193 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1351,10 +1351,10 @@ ssize_t 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; @@ -1375,10 +1375,10 @@ ssize_t 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