| Message ID | 20210111130251.361335-3-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 9f65df9c589f249435255da37a5dd11f1bc86f4d |
| Headers | show |
| Series | ALSA: firewire: Fix integer overflows on 32-bit | expand |
Hi, On Mon, Jan 11, 2021 at 02:02:51PM +0100, Geert Uytterhoeven wrote: > As snd_fw_async_midi_port.consume_bytes is unsigned int, and > NSEC_PER_SEC is 1000000000L, the second multiplication in > > port->consume_bytes * 8 * NSEC_PER_SEC / 31250 > > always overflows on 32-bit platforms, truncating the result. Fix this > by precalculating "NSEC_PER_SEC / 31250", which is an integer constant. > > Note that this assumes port->consume_bytes <= 16777. > > Fixes: 531f471834227d03 ("ALSA: firewire-lib/firewire-tascam: localize async midi port") > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Compile-tested only. > > I don't know the maximum transfer length of MIDI, but given it's an old > standard, I guess it's rather small. If it is larger than 16777, the > constant "8" should be replaced by "8ULL", to force 64-bit arithmetic. > --- > sound/firewire/tascam/tascam-transaction.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Indeed. The calculation brings integer overflow of 32 bit storage. Thanks for your care and proposal of the patch. I agree with the intension of patch, however I have a nitpicking that the consume_bytes member is defined as 'int', not 'unsigned int' in your commit comment. The member has value returned from the call of 'fill_message()'[1] for the length of byte messages in buffer to process, or for error code. The error code is checked immediately. The range of value is equal to or less than 3 when reaching the calculation, thus it should be less than 16777. Regardless of the type of 'int' or 'unsigned int', this patch can fix the issued problem. Feel free to add my tag when you post second version with comment fix. Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> > diff --git a/sound/firewire/tascam/tascam-transaction.c b/sound/firewire/tascam/tascam-transaction.c > index 90288b4b46379526..a073cece4a7d5e3a 100644 > --- a/sound/firewire/tascam/tascam-transaction.c > +++ b/sound/firewire/tascam/tascam-transaction.c > @@ -209,7 +209,7 @@ static void midi_port_work(struct work_struct *work) > > /* Set interval to next transaction. */ > port->next_ktime = ktime_add_ns(ktime_get(), > - port->consume_bytes * 8 * NSEC_PER_SEC / 31250); > + port->consume_bytes * 8 * (NSEC_PER_SEC / 31250)); > > /* Start this transaction. */ > port->idling = false; > -- > 2.25.1 [1] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/tree/sound/firewire/tascam/tascam-transaction.c#n197 Thanks Takashi Sakamoto
Hi Sakamoto-san, On Tue, Jan 12, 2021 at 2:43 PM Takashi Sakamoto <o-takashi@sakamocchi.jp> wrote: > On Mon, Jan 11, 2021 at 02:02:51PM +0100, Geert Uytterhoeven wrote: > > As snd_fw_async_midi_port.consume_bytes is unsigned int, and > > NSEC_PER_SEC is 1000000000L, the second multiplication in > > > > port->consume_bytes * 8 * NSEC_PER_SEC / 31250 > > > > always overflows on 32-bit platforms, truncating the result. Fix this > > by precalculating "NSEC_PER_SEC / 31250", which is an integer constant. > > > > Note that this assumes port->consume_bytes <= 16777. > > > > Fixes: 531f471834227d03 ("ALSA: firewire-lib/firewire-tascam: localize async midi port") > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > > --- > > Compile-tested only. > > > > I don't know the maximum transfer length of MIDI, but given it's an old > > standard, I guess it's rather small. If it is larger than 16777, the > > constant "8" should be replaced by "8ULL", to force 64-bit arithmetic. > > --- > > sound/firewire/tascam/tascam-transaction.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > Indeed. The calculation brings integer overflow of 32 bit storage. Thanks > for your care and proposal of the patch. I agree with the intension of > patch, however I have a nitpicking that the consume_bytes member is > defined as 'int', not 'unsigned int' in your commit comment. Thanks, you're right. Note that port->consume_bytes being signed halves the limit to 8388 bytes, which is of course still met. > The member has value returned from the call of 'fill_message()'[1] for the > length of byte messages in buffer to process, or for error code. The > error code is checked immediately. The range of value is equal to > or less than 3 when reaching the calculation, thus it should be less than > 16777. > > Regardless of the type of 'int' or 'unsigned int', this patch can fix > the issued problem. Feel free to add my tag when you post second version > with comment fix. > > Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Thanks! Gr{oetje,eeting}s, Geert
On Mon, 11 Jan 2021 14:02:51 +0100, Geert Uytterhoeven wrote: > > As snd_fw_async_midi_port.consume_bytes is unsigned int, and > NSEC_PER_SEC is 1000000000L, the second multiplication in > > port->consume_bytes * 8 * NSEC_PER_SEC / 31250 > > always overflows on 32-bit platforms, truncating the result. Fix this > by precalculating "NSEC_PER_SEC / 31250", which is an integer constant. > > Note that this assumes port->consume_bytes <= 16777. > > Fixes: 531f471834227d03 ("ALSA: firewire-lib/firewire-tascam: localize async midi port") > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Compile-tested only. > > I don't know the maximum transfer length of MIDI, but given it's an old > standard, I guess it's rather small. If it is larger than 16777, the > constant "8" should be replaced by "8ULL", to force 64-bit arithmetic. Applied now. Thanks. Takashi
diff --git a/sound/firewire/tascam/tascam-transaction.c b/sound/firewire/tascam/tascam-transaction.c index 90288b4b46379526..a073cece4a7d5e3a 100644 --- a/sound/firewire/tascam/tascam-transaction.c +++ b/sound/firewire/tascam/tascam-transaction.c @@ -209,7 +209,7 @@ static void midi_port_work(struct work_struct *work) /* Set interval to next transaction. */ port->next_ktime = ktime_add_ns(ktime_get(), - port->consume_bytes * 8 * NSEC_PER_SEC / 31250); + port->consume_bytes * 8 * (NSEC_PER_SEC / 31250)); /* Start this transaction. */ port->idling = false;
As snd_fw_async_midi_port.consume_bytes is unsigned int, and NSEC_PER_SEC is 1000000000L, the second multiplication in port->consume_bytes * 8 * NSEC_PER_SEC / 31250 always overflows on 32-bit platforms, truncating the result. Fix this by precalculating "NSEC_PER_SEC / 31250", which is an integer constant. Note that this assumes port->consume_bytes <= 16777. Fixes: 531f471834227d03 ("ALSA: firewire-lib/firewire-tascam: localize async midi port") Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- Compile-tested only. I don't know the maximum transfer length of MIDI, but given it's an old standard, I guess it's rather small. If it is larger than 16777, the constant "8" should be replaced by "8ULL", to force 64-bit arithmetic. --- sound/firewire/tascam/tascam-transaction.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)