linux-kernel - [PATCH] tee: shm: fix use-after-free via temporarily dropped reference

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20180507095841.6452-1-jens.wiklander@linaro.org>
Date:   Mon,  7 May 2018 11:58:41 +0200
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        tee-dev@...ts.linaro.org
Cc:     Jann Horn <jannh@...gle.com>,
        Jens Wiklander <jens.wiklander@...aro.org>
Subject: [PATCH] tee: shm: fix use-after-free via temporarily dropped reference

From: Jann Horn <jannh@...gle.com>

Bump the file's refcount before moving the reference into the fd table,
not afterwards. The old code could drop the file's refcount to zero for a
short moment before calling get_file() via get_dma_buf().

This code can only be triggered on ARM systems that use Linaro's OP-TEE.

Fixes: 967c9cca2cc5 ("tee: generic TEE subsystem")
Signed-off-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
---
 drivers/tee/tee_shm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 556960a1bab3..07d3be6f0780 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -360,9 +360,10 @@ int tee_shm_get_fd(struct tee_shm *shm)
 	if (!(shm->flags & TEE_SHM_DMA_BUF))
 		return -EINVAL;
 
+	get_dma_buf(shm->dmabuf);
 	fd = dma_buf_fd(shm->dmabuf, O_CLOEXEC);
-	if (fd >= 0)
-		get_dma_buf(shm->dmabuf);
+	if (fd < 0)
+		dma_buf_put(shm->dmabuf);
 	return fd;
 }
 
-- 
2.17.0