At Thu, 23 Jan 2014 09:36:24 +0100, Takashi Iwai wrote:

At Thu, 23 Jan 2014 11:21:28 +0300, Dan Carpenter wrote:

...

The test here is intended intended to prevent shift wrapping bugs when we do "1U << idx2". We should consider the number of bits in a u32 instead of the number of bytes.

Fixes: 7bb2491b35a2 ('ALSA: Add kconfig to specify the max card numbers') Signed-off-by: Dan Carpenter dan.carpenter@oracle.com

---

WARNING: Please check this one carefully because I might be wrong.

You're correct. I obviously didn't test more than 4. Applied (with Cc to stable) now, thanks.

I found there is another place doing it wrongly (a few lines above there), so fixed similarly in the same patch.

(And, yes, the code should be refactored; the patch will be sent soon later.)

Takashi

-- 8< -- From: Dan Carpenter dan.carpenter@oracle.com Subject: [PATCH] ALSA: bits vs bytes bug in snd_card_create()

The test here is intended intended to prevent shift wrapping bugs when we do "1U << idx2". We should consider the number of bits in a u32 instead of the number of bytes.

[fix another chunk similarly by tiwai]

Fixes: 7bb2491b35a2 ('ALSA: Add kconfig to specify the max card numbers') Signed-off-by: Dan Carpenter dan.carpenter@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/core/init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/core/init.c b/sound/core/init.c index 1351f22f651c..e3c93cd77ee7 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -170,7 +170,7 @@ int snd_card_create(int idx, const char *xid, if (idx < 0) { for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++) { /* idx == -1 == 0xffff means: take any free slot */ - if (idx2 < sizeof(int) && !(idx & (1U << idx2))) + if (idx2 < 32 && !(idx & (1U << idx2))) continue; if (!test_bit(idx2, snd_cards_lock)) { if (module_slot_match(module, idx2)) { @@ -183,7 +183,7 @@ int snd_card_create(int idx, const char *xid, if (idx < 0) { for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++) { /* idx == -1 == 0xffff means: take any free slot */ - if (idx2 < sizeof(int) && !(idx & (1U << idx2))) + if (idx2 < 32 && !(idx & (1U << idx2))) continue; if (!test_bit(idx2, snd_cards_lock)) { if (!slots[idx2] || !*slots[idx2]) {

At Thu, 23 Jan 2014 09:55:31 +0100, walter harms wrote:

Am 23.01.2014 09:21, schrieb Dan Carpenter:

...

The test here is intended intended to prevent shift wrapping bugs when we do "1U << idx2". We should consider the number of bits in a u32 instead of the number of bytes.

Fixes: 7bb2491b35a2 ('ALSA: Add kconfig to specify the max card numbers') Signed-off-by: Dan Carpenter dan.carpenter@oracle.com

---

WARNING: Please check this one carefully because I might be wrong.

diff --git a/sound/core/init.c b/sound/core/init.c index 1351f22f651c..e9e3db321e64 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -183,7 +183,7 @@ int snd_card_create(int idx, const char *xid, if (idx < 0) { for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++) { /* idx == -1 == 0xffff means: take any free slot */

• 	if (idx2 < sizeof(int) && !(idx & (1U << idx2)))
  

• 	if (idx2 < 32 && !(idx & (1U << idx2)))
  	continue;
  if (!test_bit(idx2, snd_cards_lock)) {
  	if (!slots[idx2] || !*slots[idx2]) {
  

--

Funny bug, to be 100% sure you could multiply by CHAR_BIT ;)

other code simple does (1UL << (nr & 31)) on the other side a check like:

#if SNDRV_CARDS > 32 # error to much sound #endif

whould give the user a hint what is going on instead of silently ignoring that error.

SNDRV_CARDS can be more than 32. That's why the check was introduced.

Takashi