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 86EAE4EDCB5; Tue, 29 Sep 2026 09:08:37 +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=1790672935; cv=none; b=jbRO4nS5UZ7jxHu5mqc72zoMCFl6hE6T3C0vF+17US1qm57RrvobNIeLyqzHtbusasyNCHle78wdIAZBaYvPD7gp3dL9uHz9SQByA+oYsXQ0q3GEx05hhHhZ68yTzt9Bv4CxJ2SOOdcGBRSSWmskJz9KZyGPStz62LuvieR/mfk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790672935; c=relaxed/simple; bh=hUqu+z+NpsvZRkjRDJy9FdbY36uS+XGX7HQYMrr7A5I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sv4UlFZE6cwrQR8rd5+S5q6jgX4RMyziCidZ5nLWN8FleyHYPReKh0Mjy0buxzUdR+12OXzUdT3ekVmZFjO+BlYislF1L6Q5LgNMncNetnfinh/lBm9u3ok7LKAdUYqwdvL2HmKbTRNOzF9Z0yKu0oSEkZ1yi+kU5KGBD0Qzl/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Gi31GtQZ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Gi31GtQZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 839BF1F00899; Tue, 29 Sep 2026 09:08:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790672915; bh=biKdnORbKSIiIJtm0MtyDDJXFakWvleESeK3nHzzGls=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Gi31GtQZrwuoT2OYzHsE3ewijr4oBOB5eTN/VKQUeoPEA/lwtbg/YzGd8DAXV/ugw RZL9xy4RAvEBXAhOfi8coHgqHKuZe0th6f+IPNo5xEr1QlwY2wTIZMwFannFF70WBR wzvgEQcaKrMJffOwp3AwMuFiSEfM/aF2ThhFC8ckpm7/3GQRhE4C9Fyd4sG+LXZ40+ T6ZQcUQciRo8SEQ5PUMqEyGxZm1nd3T1rnVDGmXcQzyJQjkRgP1YzzSfEfQavHkC2x ujeI/+pWRwOVr0KDdOMB3JpenPzpirA1w6TSF2A8AZueG7mHHiZjed3iO+0In8ygqe g60vrPCEjw+pQ== From: Lee Jones To: lee@kernel.org, Alexander Viro , Greg Kroah-Hartman , Jeff Layton , Christian Brauner , Peter Zijlstra , Andrew Morton , Soheil Hassas Yeganeh , Davidlohr Bueso , Paolo Abeni , Eric Dumazet , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Linus Torvalds , Quentin Schulz , Wentao Guan Subject: [STABLE v5.15.y v2 4/9] eventpoll: split __ep_remove() Date: Tue, 29 Sep 2026 09:07:11 +0000 Message-ID: <20260929090724.1461557-4-lee@kernel.org> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog In-Reply-To: <20260929090724.1461557-1-lee@kernel.org> References: <20260929090724.1461557-1-lee@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Christian Brauner [ Upstream commit 0f7bdfd413000985de09fc39eb9efa1e091a3ce0 ] Split __ep_remove() to delineate file removal from epoll item removal. Suggested-by: Linus Torvalds Link: https://patch.msgid.link/20260423-work-epoll-uaf-v1-2-2470f9eec0f5@kernel.org Signed-off-by: Christian Brauner (Amutable) Stable-dep-of: a6dc643c6931 ("eventpoll: fix ep_remove struct eventpoll / struct file UAF") Signed-off-by: Quentin Schulz Signed-off-by: Wentao Guan Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 66bc7c8a33df3618e43ce0d0d4a985595ce57861) Signed-off-by: Lee Jones --- fs/eventpoll.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 4a39ed132c3d..b6d1a939bd1d 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -708,6 +708,9 @@ static void ep_free(struct eventpoll *ep) kfree_rcu(ep, rcu); } +static void __ep_remove_file(struct eventpoll *ep, struct epitem *epi, struct file *file); +static bool __ep_remove_epi(struct eventpoll *ep, struct epitem *epi); + /* * Removes a "struct epitem" from the eventpoll RB tree and deallocates * all the associated resources. Must be called with "mtx" held. @@ -719,8 +722,6 @@ static void ep_free(struct eventpoll *ep) static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) { struct file *file = epi->ffd.file; - struct epitems_head *to_free; - struct hlist_head *head; lockdep_assert_irqs_enabled(); @@ -736,8 +737,21 @@ static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) return false; } - to_free = NULL; - head = file->f_ep; + __ep_remove_file(ep, epi, file); + return __ep_remove_epi(ep, epi); +} + +/* + * Called with &file->f_lock held, + * returns with it released + */ +static void __ep_remove_file(struct eventpoll *ep, struct epitem *epi, struct file *file) +{ + struct epitems_head *to_free = NULL; + struct hlist_head *head = file->f_ep; + + lockdep_assert_held(&ep->mtx); + if (hlist_is_singular_node(&epi->fllink, head)) { /* See eventpoll_release() for details. */ WRITE_ONCE(file->f_ep, NULL); @@ -751,6 +765,11 @@ static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) hlist_del_rcu(&epi->fllink); spin_unlock(&file->f_lock); free_ephead(to_free); +} + +static bool __ep_remove_epi(struct eventpoll *ep, struct epitem *epi) +{ + lockdep_assert_held(&ep->mtx); rb_erase_cached(&epi->rbn, &ep->rbr); -- 2.56.0.rc1.315.gc6ed9934b7-goog