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=1793209966; b=N6h26u3qOCoqvL177R4XKRpM9Gtr9l4p6kdS+9Yqt7Cl6KGsoCEXEkDJb/OSNL9dRZIG Mkc1fRWGH11FnaQuwfob+KRdh4vDAto/jrtfhTdM5foe2y+ANXByBD8QJvvdzaVtAI1Sf wzdVyO8p1I3MWiL6LU1+xFvmM84kNG6M7GyHjKFa4cROMuXv17EGhjsbtvHY5/wORaJc7 OaxBHVL6gYStUWsMAAQDliVCC1eZebDxUCBPv3w0PApL6p3mNPRCGTlBADBwsHuRmAWsG 3RJSEzvcClZpqdmk+hZI7AB6GrJj6SeDmaFsaxsz9TkysI+8HSNg+SQ3WhdViDb2NDQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793209966; 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=cngq/ugPpuzolfit3VfE638GDAtAw5BJ/tTUh9REWKY=; b=ctDkDXEQkb28/fLSARi73HQvjynbsnKExp2Ir+k6xHRkz4X6NX90tQKfoGIdvDaVjkjk lpI15YpFD8gOYZBWIxq93Lbuq3UK7+uu3AiathArgdFgw4alPx9NSPG5UbPkKbI9JPT88 9xMbBZHduuZezQ0FsmQeoyci4gjEsFkDK9O5IHQ76jzJxEuWTRi+C7fkxWixBS+CHyDHs XK+0EHU+MFR/wb0nmaeogpGj78JkNy/sVW8T8LJF1ZlHMNg0EtoVfRV8BstTDIXpXWD1k YFdUUiqZ19ZV8kQK1xoBTXN10RESitDXJbzKl27AassFZ9W6Xh5oaLSYB3IDlcPYZig== 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=McKfsOe9; 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 AD835606A31A; Wed, 28 Oct 2026 17:52:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=McKfsOe9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB3521F01825; Wed, 28 Oct 2026 17:52:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793209965; bh=cngq/ugPpuzolfit3VfE638GDAtAw5BJ/tTUh9REWKY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=McKfsOe9k0dn2KFwUdf8D8/XRt8TImFg36nwWdGH9mHm5urUt/Cqxt4xgajuPCDZK OqA2e0SZtxhPHAI7vlF95lFdXmGXDRSMdrhoepucChXXOt9MpDfIyyQPxsBWFQ7m50 zs1YTuzzw5ImJwSTiLemzXZmfUa8q0NlVzPBV1es= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kyle Zeng , "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.6 029/168] pipe: preserve existing fasync readers on writer setup failure Date: Wed, 28 Oct 2026 17:59:25 +0100 Message-ID: <20261028165943.787618264@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165943.089486480@linuxfoundation.org> References: <20261028165943.089486480@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kyle Zeng [ Upstream commit 40bb03d3ea6f6a915218508819ecc4d7a7fa260d ] F_SETFL and FIOASYNC decide whether to invoke ->fasync() before pipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can therefore both enter the callback. fasync_helper() allocates before checking for an existing entry. If the first enable installs both entries, a second enable can update the reader entry and then fail the allocation for the writer entry. The error path removes the pre-existing reader entry, clearing FASYNC while the writer entry remains registered. __fput() then skips ->fasync(), so a later pipe notification can dereference the freed file or its f_owner. An unprivileged memory-pressure reproducer triggers a KASAN slab-use-after-free in send_sigio() through this path. Keep the reader helper's result and undo the registration only if this call added it. The pipe mutex serializes changes to both lists, so a failed new registration still removes its reader, while a failed duplicate preserves the existing registrations and FASYNC. Successful duplicate enables continue to update fa_fd as before. Fixes: 76398425bb06 ("Move FASYNC bit handling to f_op->fasync()") Signed-off-by: Kyle Zeng Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Sasha Levin --- fs/pipe.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index ba4376341ddd2..2ad7eba72b35a 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -751,9 +751,11 @@ pipe_fasync(int fd, struct file *filp, int on) if (filp->f_mode & FMODE_READ) retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { + int read_ret = retval; + retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); - if (retval < 0 && (filp->f_mode & FMODE_READ)) - /* this can happen only if on == T */ + /* Undo only a reader entry added by this call. */ + if (retval < 0 && read_ret > 0) fasync_helper(-1, filp, 0, &pipe->fasync_readers); } __pipe_unlock(pipe); -- 2.53.0