Re: [PATCH] ALSA: hda/core: fix memory leak in snd_hdac_bus_alloc_stream_pages()

[Zhao Dongdong]

On Mon, 06 Jul 2026 12:19:22 +0200, Takashi Iwai <tiwai@xxxxxxx> wrote:
>
> On Mon, 06 Jul 2026 10:51:11 +0200,
> Zhao Dongdong wrote:
> > 
> > On Mon, 06 Jul 2026 10:11:56 +0200, Takashi Iwai <tiwai@xxxxxxx> wrote:
> > >
> > > On Mon, 06 Jul 2026 09:41:10 +0200,
> > > Zhao Dongdong wrote:
> > > > 
> > > > From: Zhao Dongdong <zhaodongdong@xxxxxxxxxx>
> > > > 
> > > > In snd_hdac_bus_alloc_stream_pages(), there are three memory leak paths:
> > > > 
> > > >   1. If snd_dma_alloc_pages() for the BDL fails at stream i, the
> > > >      previously allocated BDL DMA buffers (0..i-1) are not freed.
> > > > 
> > > >   2. If snd_dma_alloc_pages() for the position buffer fails, all
> > > >      previously allocated BDL DMA buffers are leaked.
> > > > 
> > > >   3. If snd_dma_alloc_pages() for the ring buffer fails, all
> > > >      previously allocated BDL DMA buffers and the position buffer
> > > >      are leaked.
> > > > 
> > > > Add proper error cleanup: free buffers that have been allocated
> > > > before each failure point.
> > > > 
> > > > Fixes: b2660d1ebde1 ("ALSA: hda: Move HD-audio core stuff into sound/hda/core")
> > > > Signed-off-by: Zhao Dongdong <zhaodongdong@xxxxxxxxxx>
> > >
> > > They don't actually leak, as those are supposed to be released by
> > > callers (via snd_hdac_bus_free_stream_pages() call at destructor).
> > > That is, it's no bug, per se.
> > >
> > > Of course, it won't be bad to clean up in the function itself, which
> > > is more self-contained and safer.  But please rephrase the patch
> > > subject and description, so that it won't be taken as a security issue
> > > incorrectly.
> > >
> > >
> > > thanks,
> > >
> > > Takashi
> > 
> > Thanks for your review. 
> > You are right that snd_hdac_bus_alloc_stream_pages and snd_hdac_bus_free_stream_pages 
> > are paired, so the extra free call is unnecessary, please ignore this patch.
>
> Well, your code change itself is fine as a code hardening, and I'll
> happily apply if the patch subject and description are updated.
> So, feel free to resubmit with the updated description.
>
>
> thanks,
>
> Takashi

Thanks. Will update the subject/description and resubmit.


-- 
Regards,
    Zhao Dongdong