On Tue, May 13, 2025 at 09:58:24AM +0530, Ekansh Gupta wrote:
> 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 any other thread removes the entry
> from list while unmap operation is ongoing. Remove the entry before
> calling unmap operation.
>
> Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support")
> Cc: sta...@kernel.org
> Signed-off-by: Ekansh Gupta <ekansh.gu...@oss.qualcomm.com>
> ---
> drivers/misc/fastrpc.c | 29 ++++++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index b629e24f00bc..d54368bf8c5c 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1868,9 +1868,6 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user
> *fl, struct fastrpc_buf *
> &args[0]);
> if (!err) {
> dev_dbg(dev, "unmmap\tpt 0x%09lx OK\n", buf->raddr);
> - spin_lock(&fl->lock);
> - list_del(&buf->node);
> - spin_unlock(&fl->lock);
> fastrpc_buf_free(buf);
> } else {
> dev_err(dev, "unmmap\tpt 0x%09lx ERROR\n", buf->raddr);
> @@ -1884,13 +1881,15 @@ static int fastrpc_req_munmap(struct fastrpc_user
> *fl, char __user *argp)
> struct fastrpc_buf *buf = NULL, *iter, *b;
> struct fastrpc_req_munmap req;
> struct device *dev = fl->sctx->dev;
> + int err;
>
> if (copy_from_user(&req, argp, sizeof(req)))
> return -EFAULT;
>
> spin_lock(&fl->lock);
> list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
> - if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
> + if (iter->raddr == req.vaddrout && iter->size == req.size) {
Cosmetics, please drop.
> + list_del(&iter->node);
> buf = iter;
> break;
> }
> @@ -1903,7 +1902,14 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl,
> char __user *argp)
> return -EINVAL;
> }
>
> - return fastrpc_req_munmap_impl(fl, buf);
> + err = fastrpc_req_munmap_impl(fl, buf);
> + if (err) {
> + spin_lock(&fl->lock);
> + list_add_tail(&buf->node, &fl->mmaps);
> + spin_unlock(&fl->lock);
> + }
> +
> + return err;
> }
>
> static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
> @@ -1997,14 +2003,23 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl,
> char __user *argp)
>
> if (copy_to_user((void __user *)argp, &req, sizeof(req))) {
> err = -EFAULT;
> - goto err_assign;
> + goto err_copy;
> }
>
> dev_dbg(dev, "mmap\t\tpt 0x%09lx OK [len 0x%08llx]\n",
> buf->raddr, buf->size);
>
> return 0;
> -
Please keep the empty line here, it improves readability.
> +err_copy:
> + if (req.flags == ADSP_MMAP_REMOTE_HEAP_ADDR) {
> + spin_lock_irqsave(&fl->cctx->lock, flags);
> + list_del(&buf->node);
> + spin_unlock_irqrestore(&fl->cctx->lock, flags);
> + } else {
> + spin_lock(&fl->lock);
> + list_del(&buf->node);
> + spin_unlock(&fl->lock);
> + }
Can we store the spinlock pointer in the struct fastrpc_buf instead?
> err_assign:
> fastrpc_req_munmap_impl(fl, buf);
>
> --
> 2.34.1
>
--
With best wishes
Dmitry
