Re: [PATCH] ALSA: usb-audio: qcom: Free sideband sg_table objects

[Takashi Iwai <tiwai@suse.de>]

On Tue, 16 Jun 2026 13:59:16 +0200,
raoxu wrote:
> 
> From: Xu Rao <raoxu@uniontech.com>
> 
> The Qualcomm USB audio offload driver obtains an endpoint transfer-ring
> table by calling xhci_sideband_get_endpoint_buffer(). This getter passes
> the endpoint ring to xhci_ring_to_sgtable(), which allocates the outer
> struct sg_table with kzalloc_obj(*sgt). The event-ring path is
> equivalent: xhci_sideband_get_event_buffer() also returns the result of
> xhci_ring_to_sgtable().
> 
> Inside xhci_ring_to_sgtable(), sg_alloc_table_from_pages() separately
> allocates the scatterlist storage referenced by sgt->sgl. The returned
> object therefore has two allocation layers: the outer struct sg_table
> and its internal scatterlist storage.
> 
> The Qualcomm caller only invokes sg_free_table(sgt). sg_free_table()
> releases the scatterlist storage owned by the table, but it does not
> free the separately allocated outer struct sg_table. The local sgt
> pointer is then discarded, so every successful endpoint or event-ring
> query leaks the outer object.
> 
> Call kfree(sgt) after sg_free_table(sgt) in both setup paths, after the
> required page and DMA addresses have been copied out.
> 
> Fixes: 326bbc348298 ("ALSA: usb-audio: qcom: Introduce QC USB SND offloading support")
> Signed-off-by: Xu Rao <raoxu@uniontech.com>

Applied now.  Thanks.


Takashi