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

[Takashi Iwai]

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