Re: [PATCH v7 2/5] misc: fastrpc: Remove buffer from list prior to unmap operation

[Dmitry Baryshkov]

On Tue, Jun 02, 2026 at 03:17:47PM +0800, Jianping Li wrote:
> From: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
> 
> fastrpc_req_munmap_impl() is called to unmap any buffer. The buffer is
> getting removed from the list after it is unmapped from DSP. This can
> create potential race conditions if multiple threads invoke unmap
> concurrently, where one thread may remove the entry from the list while
> another thread's unmap operation is still ongoing.
> 
> Fix this by removing the buffer entry from the list before calling the
> unmap operation. If the unmap fails, the entry is re-added to the list
> so that userspace can retry the unmap, or alternatively, the buffer
> will be cleaned up during device release when the DSP process is torn
> down and all DSP-side mappings are freed along with remaining buffers
> in the list.
> 
> Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
> Signed-off-by: Jianping Li <jianping.li@xxxxxxxxxxxxxxxx>
> ---
>  drivers/misc/fastrpc.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>


-- 
With best wishes
Dmitry