Guard against wrap-around in alloc functions
Because of the exposed nature of the libjpeg API, alloc_small() and
alloc_large() can potentially be called by external code. If an
application were to call either of those functions with
sizeofobject > SIZE_MAX - ALIGN_SIZE - 1, then the math in
round_up_pow2() would wrap around to zero, causing that function to
return a small value. That value would likely not exceed
MAX_ALLOC_CHUNK, so the subsequent size checks in alloc_small() and
alloc_large() would not catch the error.
A similar problem could occur in 32-bit builds if alloc_sarray() were
called with
samplesperrow > SIZE_MAX - (2 * ALIGN_SIZE / sizeof(JSAMPLE)) - 1
This patch simply ensures that the size argument to the alloc_*()
functions will never exceed MAX_ALLOC_CHUNK (1 billion). If it did,
then subsequent size checks would eventually catch that error, so we
are instead catching the error before round_up_pow2() is called.
This addresses a minor concern (LJT-01-001) expressed in a security
audit by Cure53.
1 file changed
