### ALSA: pcm: fix delta calculation at boundary wraparound

In the cleanup of the hw_ptr update functions in 2.6.33, the calculation of the delta value was changed to use the modulo operator to protect against a negative difference due to the pointer wrapping around at the boundary. However, the ptr variables are unsigned, so a negative difference would result in the two complement's value which has no relation to the actual difference relative to the boundary; the result is typically some value near LONG_MAX-boundary. Furthermore, even if the modulo operation would be done with signed types, the result of a negative dividend could be negative. The invalid delta value is then caught by the following checks, but this means that the pointer update is ignored. To fix this, use a range check as in the other pointer calculations. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Cc: <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>

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