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=1794412741; b=ibtL9xyZJtr1y8uhwJ0oampwf/CoETQlaDbpVsEedpQQQlCQ7W/5pFrxZ4kNU6tR3aiW VwML3rOUad6VyS4s8AOQDtK1jPGMSdNLJBy7hiqpaXbO9xPnBYVO+hAZPh4c+uIsrAaWp CnHkHCWYaKOTJYLo/nwZOfDL5mqVt9JASg7ZnUxhzYL48AaRBy5z0JqdggPZ/b+RvhFd8 AeAbUmtB/hukokythhWf6g3HbmIi560BYRgi5hvrRgOEV1xk0VprX/MIqVOiwUe3GD+Fc ChmG8KLs6okRvRI+0Rmr486FYC7+chJbO4gChi5GB7CbZN+g1yvVREJcIGLbPVY2rQA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794412741; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=oImOupv6sF18dten5DgH8uCzzPA7MNXQ5UprHlFCaQ4=; b=nkqNfDZ7pfU7qaas/Ff6UTCDR8Kyz6mrOlv6m3TzLaAbGNzxpRNhcq2dGwVQVjtr7nKV 9rLdAaq9dj+spea3yrDA6GRS2qddqWuTRcwY+5Uy42+RBlORQyil+NKQPCgRxHgs3voIX 4K08kCD8DNKvRckE4VZLclPYFrXTrXjz3l9sS3qJOQx2RAX/6BC/lyPACp3L4+D+Uiig6 fBAG8N7dBalq3ZosPKRdU5p7kFpmFBS+/I3mbV6f0YSXCLhqbGr5s6MmnGKMPqxhYTFp0 Ci0k6hj9NP8nehP0u7Jpn0ktDEVgv5qdIZePDiAtuKHsLVQtqKJxVrhAec0zod1JqPw== 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=WaND8zGe; 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 6BC6F606A32E for ; Wed, 11 Nov 2026 15:59:01 +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=WaND8zGe Received: by smtp.kernel.org (Postfix) with ESMTPSA id C284C1F00A07; Wed, 11 Nov 2026 15:59:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794412741; bh=oImOupv6sF18dten5DgH8uCzzPA7MNXQ5UprHlFCaQ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WaND8zGeFoxOmWGem4VWOTJ4RA8SKCYRuSsBL1z8ezNIgmPHai7yj0cCKHv+wo575 XpSu/p7Ah5aHfcPC+20T/wVIe/CPlQIt/3BeubPUiFXPpnGAL/aYdzTZPBxnGbwYKp XRSjV/RVb4gibwNDZpryt39T8LQ09XO7pWZI1V1wqPyxzdiRwOzZhDdKFezf2SPMdD RjOS/TotS9IxIe5uOx6Kk2Aa1uiWUxlB1Fiji+hV/jPRTtLnG5oAEzaMRSQtmTxUTR T03E4xx2+6abW6K2rfdOOBH/Ll+L/XoIv9sr805PQRdcwb/vI9dwW3trldBBdqhC0j 7RhGG1k8iFn/A== From: Sasha Levin To: stable@vger.kernel.org Cc: Daehyeon Ko <4ncienth@gmail.com>, "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 5.15.y 3/3] splice: avoid stale f_pos writeback on error Date: Wed, 11 Nov 2026 10:58:57 -0500 Message-ID: <20261111155849.2761399-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261111155849.2761399-1-sashal@kernel.org> References: <20261107061356-failed-5.15-79b496ebe382@kernel.org> <20261111155849.2761399-1-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 70008e08998f5..3630fd18a12e8 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1107,10 +1107,10 @@ 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; @@ -1127,10 +1127,10 @@ 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