random: check for increase of entropy_count because of signed conversion
The expression entropy_count -= ibytes << (ENTROPY_SHIFT + 3) could actually increase entropy_count if during assignment of the unsigned expression on the RHS (mind the -=) we reduce the value modulo 2^width(int) and assign it to entropy_count. Trinity found this. [ Commit modified by tytso to add an additional safety check for a negative entropy_count -- which should never happen, and to also add an additional paranoia check to prevent overly large count values to be passed into urandom_read(). ] Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
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