Re: [PATCH] firmware_loader: fix memory leak for paged buffer

[Takashi Iwai]

On Wed, 12 Aug 2020 21:00:19 +0200,
Prateek Sood wrote:
> 
> vfree() is being called on paged buffer allocated
> using alloc_page() and mapped using vmap().
> 
> Freeing of pages in vfree() relies on nr_pages of
> struct vm_struct. vmap() does not update nr_pages.
> It can lead to memory leaks.
> 
> Signed-off-by: Prateek Sood <prs...@codeaurora.org>

Thanks for spotting this out!  This is essentially a revert of the
commit ddaf29fd9bb6 ("firmware: Free temporary page table after
vmapping"), so better to mention it via Fixes tag as well as Cc to
stable.

About the changes:
> --- a/drivers/base/firmware_loader/firmware.h
> +++ b/drivers/base/firmware_loader/firmware.h
> @@ -142,10 +142,12 @@ static inline void fw_state_done(struct fw_priv 
> *fw_priv)
>  void fw_free_paged_buf(struct fw_priv *fw_priv);
>  int fw_grow_paged_buf(struct fw_priv *fw_priv, int pages_needed);
>  int fw_map_paged_buf(struct fw_priv *fw_priv);
> +bool fw_is_paged_buf(struct fw_priv *fw_priv);

I guess this isn't necessary if we just swap the call order of
fw_free_paged_buf() and vfree(); then fw_priv->is_paged_buf is
referred only in fw_free_paged_buf().
That is, something like below.

In anyway, take my review tag:
  Reviewed-by: Takashi Iwai <ti...@suse.de>


thanks,

Takashi

--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -252,9 +252,9 @@ static void __free_fw_priv(struct kref *ref)
        list_del(&fw_priv->list);
        spin_unlock(&fwc->lock);
 
-       fw_free_paged_buf(fw_priv); /* free leftover pages */
        if (!fw_priv->allocated_size)
                vfree(fw_priv->data);
+       fw_free_paged_buf(fw_priv); /* free leftover pages */
        kfree_const(fw_priv->fw_name);
        kfree(fw_priv);
 }
@@ -272,7 +272,7 @@ void fw_free_paged_buf(struct fw_priv *fw_priv)
 {
        int i;
 
-       if (!fw_priv->pages)
+       if (!fw_priv->is_paged_buf)
                return;
 
        for (i = 0; i < fw_priv->nr_pages; i++)
@@ -328,10 +328,6 @@ int fw_map_paged_buf(struct fw_priv *fw_priv)
        if (!fw_priv->data)
                return -ENOMEM;
 
-       /* page table is no longer needed after mapping, let's free */
-       kvfree(fw_priv->pages);
-       fw_priv->pages = NULL;
-
        return 0;
 }
 #endif