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tee: shm: fix use-after-free via temporarily dropped reference

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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: 967c9cca2c ("tee: generic TEE subsystem")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
This commit is contained in:
Jann Horn 2018-04-04 21:03:21 +02:00 committed by Jens Wiklander
parent 75bc37fefc
commit bb765d1c33
1 changed files with 3 additions and 2 deletions
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drivers/tee/tee_shm.c
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@ -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;
}