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 AA19744470F; Tue, 21 Jul 2026 21:08:17 +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=1784668098; cv=none; b=fOau06BX9XytDbDwZpWThu40kuoQbiAwxPXP8Nc8jzXbKg/9K0/3mMfGwTkbodnAzCV80KL0otI50Yb7oSTyVlZQvijH7FPecQHdXexSRPZ3Mk3NyteGvc+w36Q0NtgLFNU9Ga+4Sfsa9SaaiUgxTpReqZlijJvEwKM1lWbZgyU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784668098; c=relaxed/simple; bh=3MnhKa5cEhA8IZtBcc7FX2yzqn3miJlcRMqhwqB9fvI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CTy2CBZ1Y5ssvooHH1CeXee01IWP8LkCj9q4ZOzM6emG+umRZQ9wrQdQxxc0qaxa1I47uAzAczyV1COdTRKr0CdLxnce90Z/x5v+DBFUO79/1Hc5lteT2xtM2KQUp/bMiv78lQs7F67/JLeMWd5r7AqwQhC/L+hlqkLfRAuNCN0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=G7Wg6KQh; 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="G7Wg6KQh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1AF1E1F000E9; Tue, 21 Jul 2026 21:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784668097; bh=aEeUlMOBovjMas/SPky5Xah1XjkncjrSV4tfHhIEhjA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=G7Wg6KQh/5Cd7LuTtJovK4ToOjolr60tKy1km4nEev3x551lDc9fOfNnitOcP872F AcJDEwZsQGeztC2imtTGdEXrvri2gRaJQCCYrO11v0Vfr9IRPdKNdmhOo14C1OJAqa bpmSRcjJQDFxruULpQFRetuOxGZPt5y2iCULFs0Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org, carnil@debian.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Christian Brauner (Amutable)" , Quentin Schulz , Wentao Guan Subject: [PATCH 6.1 0045/1067] eventpoll: move epi_fget() up Date: Tue, 21 Jul 2026 17:10:46 +0200 Message-ID: <20260721152425.568030744@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152424.521567757@linuxfoundation.org> References: <20260721152424.521567757@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-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") [file_ref_get(&file->f_ref) from original commit left as atomic_long_inc_not_zero(&file->f_count) due to v6.12.y missing commit 90ee6ed776c0 ("fs: port files to file_ref") and its dependent commit 08ef26ea9ab3 ("fs: add file_ref")] Signed-off-by: Quentin Schulz Signed-off-by: Wentao Guan Signed-off-by: Greg Kroah-Hartman --- fs/eventpoll.c | 56 ++++++++++++++++++++++++++++---------------------------- 1 file changed, 28 insertions(+), 28 deletions(-) --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -716,6 +716,34 @@ static void ep_free(struct eventpoll *ep } /* + * 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 (!atomic_long_inc_not_zero(&file->f_count)) + file = NULL; + return file; +} + +/* * Called with &file->f_lock held, * returns with it released */ @@ -887,34 +915,6 @@ static __poll_t __ep_eventpoll_poll(stru } /* - * 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 (!atomic_long_inc_not_zero(&file->f_count)) - 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() * is correctly annotated.