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SubjectRe: [PATCH] firmware_loader: fix memory leak for paged buffer
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 <prsood@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 <tiwai@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
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