From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 526A13D8918; Wed, 20 May 2026 17:05:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779296750; cv=none; b=VFCW+KjwaNf5m+JvZJsqYMrhJ+uwK5yJWuC8/JspRz/apsALYBE7GzGZVIaon+b1AlKV8ll9U8PZ6zTJAp51devUJKfgq1LBjJkPlJ6IvzBMiuVcm/840Oo9D55sA2jvH+ms4CrNSixSt7yzfQsBcANbbTY6+V5YKLGmeoQUh1U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779296750; c=relaxed/simple; bh=Iz2Fb055fya8CUAqX36r/KJ205nzk6wCwXq5PD7+xx0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sESeQZu6criWuhOXH5qm0QV1SF4EvaPt+FvQDvDCJ1ozD+pj5BRs37l0y7wwU1ZW25gJ8wLNgzoggGtLx4qgTUBhRYfXEc5x4wQvUapSmd8/5jbS2mUDUEBXkaxgFsInI2Nf28RclKp6otXcdS2iX9woV9sYZiRS4oRGE1o1EBQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=owWabZO+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="owWabZO+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29C171F000E9; Wed, 20 May 2026 17:05:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779296748; bh=U1/ZdnIJuHDo+5in/f02C+B96d+3VfZ727pLEHsA97A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=owWabZO+ULCW5VyWuWAu3OZ1rNVJT1ZDI6cbZTclJZ4ZaPVPQsnU59MssrVrM3LTa A/+F4H0LybR4a2KNdrRsE4nFb33AAiu1a3nVsGFfEu4RDpK24kePFA83IK3CMt07/Z zyLFm2DEWxKIBeU6xNY+jioPWVj3Uw4BNu7JADek= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 7.0 0866/1146] eventpoll: move epi_fget() up Date: Wed, 20 May 2026 18:18:36 +0200 Message-ID: <20260520162207.837457234@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162148.390695140@linuxfoundation.org> References: <20260520162148.390695140@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner [ Upstream commit 86e87059e6d1fd5115a31949726450ed03c1073b ] We'll need it when removing files so move it up. No functional change. Link: https://patch.msgid.link/20260423-work-epoll-uaf-v1-5-2470f9eec0f5@kernel.org Signed-off-by: Christian Brauner (Amutable) Stable-dep-of: a6dc643c6931 ("eventpoll: fix ep_remove struct eventpoll / struct file UAF") Signed-off-by: Sasha Levin --- fs/eventpoll.c | 56 +++++++++++++++++++++++++------------------------- 1 file changed, 28 insertions(+), 28 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 14bc5b355f0e2..4971074ab476a 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -826,6 +826,34 @@ static void ep_free(struct eventpoll *ep) kfree_rcu(ep, rcu); } +/* + * The ffd.file pointer may be in the process of being torn down due to + * being closed, but we may not have finished eventpoll_release() yet. + * + * Normally, even with the atomic_long_inc_not_zero, the file may have + * been free'd and then gotten re-allocated to something else (since + * files are not RCU-delayed, they are SLAB_TYPESAFE_BY_RCU). + * + * But for epoll, users hold the ep->mtx mutex, and as such any file in + * the process of being free'd will block in eventpoll_release_file() + * and thus the underlying file allocation will not be free'd, and the + * file re-use cannot happen. + * + * For the same reason we can avoid a rcu_read_lock() around the + * operation - 'ffd.file' cannot go away even if the refcount has + * reached zero (but we must still not call out to ->poll() functions + * etc). + */ +static struct file *epi_fget(const struct epitem *epi) +{ + struct file *file; + + file = epi->ffd.file; + if (!file_ref_get(&file->f_ref)) + file = NULL; + return file; +} + /* * Called with &file->f_lock held, * returns with it released @@ -1018,34 +1046,6 @@ static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int dep return res; } -/* - * The ffd.file pointer may be in the process of being torn down due to - * being closed, but we may not have finished eventpoll_release() yet. - * - * Normally, even with the atomic_long_inc_not_zero, the file may have - * been free'd and then gotten re-allocated to something else (since - * files are not RCU-delayed, they are SLAB_TYPESAFE_BY_RCU). - * - * But for epoll, users hold the ep->mtx mutex, and as such any file in - * the process of being free'd will block in eventpoll_release_file() - * and thus the underlying file allocation will not be free'd, and the - * file re-use cannot happen. - * - * For the same reason we can avoid a rcu_read_lock() around the - * operation - 'ffd.file' cannot go away even if the refcount has - * reached zero (but we must still not call out to ->poll() functions - * etc). - */ -static struct file *epi_fget(const struct epitem *epi) -{ - struct file *file; - - file = epi->ffd.file; - if (!file_ref_get(&file->f_ref)) - file = NULL; - return file; -} - /* * Differs from ep_eventpoll_poll() in that internal callers already have * the ep->mtx so we need to start from depth=1, such that mutex_lock_nested() -- 2.53.0