drm/vmwgfx: Fix stale file descriptors on failed usercopy

stable inclusion
from stable-v5.10.95
commit ae2b20f27732fe92055d9e7b350abc5cdf3e2414
bugzilla: https://gitee.com/openeuler/kernel/issues/I55EDV

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae2b20f27732fe92055d9e7b350abc5cdf3e2414



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commit a0f90c88 upstream.

A failing usercopy of the fence_rep object will lead to a stale entry in
the file descriptor table as put_unused_fd() won't release it. This
enables userland to refer to a dangling 'file' object through that still
valid file descriptor, leading to all kinds of use-after-free
exploitation scenarios.

Fix this by deferring the call to fd_install() until after the usercopy
has succeeded.

Fixes: c906965d ("drm/vmwgfx: Add export fence to file descriptor support")
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>