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dmabuf: fix use-after-free of dmabuf's file->f_inode 

It is observed 'use-after-free' on the dmabuf's file->f_inode with the
race between closing the dmabuf file and reading the dmabuf's debug
info.

Consider the below scenario where P1 is closing the dma_buf file
and P2 is reading the dma_buf's debug info in the system:

P1						P2
					dma_buf_debug_show()
dma_buf_put()
  __fput()
    file->f_op->release()
    dput()
    ....
      dentry_unlink_inode()
        iput(dentry->d_inode)
        (where the inode is freed)
					mutex_lock(&db_list.lock)
					read 'dma_buf->file->f_inode'
					(the same inode is freed by P1)
					mutex_unlock(&db_list.lock)
      dentry->d_op->d_release()-->
        dma_buf_release()
          .....
          mutex_lock(&db_list.lock)
          removes the dmabuf from the list
          mutex_unlock(&db_list.lock)

In the above scenario, when dma_buf_put() is called on a dma_buf, it
first frees the dma_buf's file->f_inode(=dentry->d_inode) and then
removes this dma_buf from the system db_list. In between P2 traversing
the db_list tries to access this dma_buf's file->f_inode that was freed
by P1 which is a use-after-free case.

Since, __fput() calls f_op->release first and then later calls the
d_op->d_release, move the dma_buf's db_list removal from d_release() to
f_op->release(). This ensures that dma_buf's file->f_inode is not
accessed after it is released.

Cc: <stable@vger.kernel.org> # 5.4.x-
Fixes: 4ab59c3c63 ("dma-buf: Move dma_buf_release() from fops to dentry_ops")
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1609857399-31549-1-git-send-email-charante@codeaurora.org
zero-sugar-mainline-defconfig
Charan Teja Reddy 2021-01-05 20:06:39 +05:30 committed by Thomas Zimmermann
parent e71ba9452f
commit 05cd84691e
1 changed files with 17 additions and 4 deletions
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21
drivers/dma-buf/dma-buf.c
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@ -76,10 +76,6 @@ static void dma_buf_release(struct dentry *dentry)
dmabuf->ops->release(dmabuf);
mutex_lock(&db_list.lock);
list_del(&dmabuf->list_node);
mutex_unlock(&db_list.lock);
if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
dma_resv_fini(dmabuf->resv);
@ -88,6 +84,22 @@ static void dma_buf_release(struct dentry *dentry)
kfree(dmabuf);
}
static int dma_buf_file_release(struct inode *inode, struct file *file)
{
struct dma_buf *dmabuf;
if (!is_dma_buf_file(file))
return -EINVAL;
dmabuf = file->private_data;
mutex_lock(&db_list.lock);
list_del(&dmabuf->list_node);
mutex_unlock(&db_list.lock);
return 0;
}
static const struct dentry_operations dma_buf_dentry_ops = {
.d_dname = dmabuffs_dname,
.d_release = dma_buf_release,
@ -413,6 +425,7 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
}
static const struct file_operations dma_buf_fops = {
.release = dma_buf_file_release,
.mmap = dma_buf_mmap_internal,
.llseek = dma_buf_llseek,
.poll = dma_buf_poll,