| Message ID | 20240522070442.17786-1-tiwai@suse.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 39381fe7394e5eafac76e7e9367e7351138a29c1 |
| Headers | show |
| Series | [1/2] ALSA: core: Fix NULL module pointer assignment at card init | expand |
On Wed, May 22, 2024 at 09:04:39AM +0200, Takashi Iwai wrote: > The commit 81033c6b584b ("ALSA: core: Warn on empty module") > introduced a WARN_ON() for a NULL module pointer passed at snd_card > object creation, and it also wraps the code around it with '#ifdef > MODULE'. This works in most cases, but the devils are always in > details. "MODULE" is defined when the target code (i.e. the sound > core) is built as a module; but this doesn't mean that the caller is > also built-in or not. Namely, when only the sound core is built-in > (CONFIG_SND=y) while the driver is a module (CONFIG_SND_USB_AUDIO=m), > the passed module pointer is ignored even if it's non-NULL, and > card->module remains as NULL. This would result in the missing module > reference up/down at the device open/close, leading to a race with the > code execution after the module removal. > > For addressing the bug, move the assignment of card->module again out > of ifdef. The WARN_ON() is still wrapped with ifdef because the > module can be really NULL when all sound drivers are built-in. > > Note that we keep 'ifdef MODULE' for WARN_ON(), otherwise it would > lead to a false-positive NULL module check. Admittedly it won't catch > perfectly, i.e. no check is performed when CONFIG_SND=y. But, it's no > real problem as it's only for debugging, and the condition is pretty > rare. > > Fixes: 81033c6b584b ("ALSA: core: Warn on empty module") > Reported-by: Xu Yang <xu.yang_2@nxp.com> > Closes: https://lore.kernel.org/r/20240520170349.2417900-1-xu.yang_2@nxp.com > Cc: <stable@vger.kernel.org> > Signed-off-by: Takashi Iwai <tiwai@suse.de> For this patchset: Tested-by: Xu Yang <xu.yang_2@nxp.com> Thanks, Xu Yang > --- > sound/core/init.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/sound/core/init.c b/sound/core/init.c > index 6b127864a1a3..ac072614d1ea 100644 > --- a/sound/core/init.c > +++ b/sound/core/init.c > @@ -313,8 +313,8 @@ static int snd_card_init(struct snd_card *card, struct device *parent, > card->number = idx; > #ifdef MODULE > WARN_ON(!module); > - card->module = module; > #endif > + card->module = module; > INIT_LIST_HEAD(&card->devices); > init_rwsem(&card->controls_rwsem); > rwlock_init(&card->ctl_files_rwlock); > -- > 2.43.0 >
diff --git a/sound/core/init.c b/sound/core/init.c index 6b127864a1a3..ac072614d1ea 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -313,8 +313,8 @@ static int snd_card_init(struct snd_card *card, struct device *parent, card->number = idx; #ifdef MODULE WARN_ON(!module); - card->module = module; #endif + card->module = module; INIT_LIST_HEAD(&card->devices); init_rwsem(&card->controls_rwsem); rwlock_init(&card->ctl_files_rwlock);
The commit 81033c6b584b ("ALSA: core: Warn on empty module") introduced a WARN_ON() for a NULL module pointer passed at snd_card object creation, and it also wraps the code around it with '#ifdef MODULE'. This works in most cases, but the devils are always in details. "MODULE" is defined when the target code (i.e. the sound core) is built as a module; but this doesn't mean that the caller is also built-in or not. Namely, when only the sound core is built-in (CONFIG_SND=y) while the driver is a module (CONFIG_SND_USB_AUDIO=m), the passed module pointer is ignored even if it's non-NULL, and card->module remains as NULL. This would result in the missing module reference up/down at the device open/close, leading to a race with the code execution after the module removal. For addressing the bug, move the assignment of card->module again out of ifdef. The WARN_ON() is still wrapped with ifdef because the module can be really NULL when all sound drivers are built-in. Note that we keep 'ifdef MODULE' for WARN_ON(), otherwise it would lead to a false-positive NULL module check. Admittedly it won't catch perfectly, i.e. no check is performed when CONFIG_SND=y. But, it's no real problem as it's only for debugging, and the condition is pretty rare. Fixes: 81033c6b584b ("ALSA: core: Warn on empty module") Reported-by: Xu Yang <xu.yang_2@nxp.com> Closes: https://lore.kernel.org/r/20240520170349.2417900-1-xu.yang_2@nxp.com Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> --- sound/core/init.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)