On Sun, May 14, 2006 at 04:20:52AM +0200, Jesper Juhl wrote:
> First testing if a pointer is NULL and if it is (or might be), proceeding
> with code that dereferences that same pointer is clearly a mistake.
> This happens in sound/isa/sb/sb8_midi.c::snd_sb8dsp_midi_interrupt()
> The patch below reworks the code so this unfortunate case doesn't happen.
All callers of snd_sb8dsp_midi_interrupt() dereference "chip" right
before calling.
> --- linux-2.6.17-rc4-git2-orig/sound/isa/sb/sb8_midi.c
> +++ linux-2.6.17-rc4-git2/sound/isa/sb/sb8_midi.c
> -irqreturn_t snd_sb8dsp_midi_interrupt(struct snd_sb * chip)
> +irqreturn_t snd_sb8dsp_midi_interrupt(struct snd_sb *chip)
> {
> struct snd_rawmidi *rmidi;
> int max = 64;
> char byte;
>
> - if (chip == NULL || (rmidi = chip->rmidi) == NULL) {
> + if (!chip)
> + return IRQ_NONE;
> +
> + rmidi = chip->rmidi;
> + if (!rmidi) {
> inb(SBP(chip, DATA_AVAIL)); /* ack interrupt */
> return IRQ_NONE;
> }
-
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