[libvirt] [PATCH] virrandom: Avoid undefined behaviour in virRandomBits
If nbits is 64 (or greater) then shifting 1ULL left is undefined. Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/util/virrandom.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/util/virrandom.c b/src/util/virrandom.c index 3c011a8615..7915f6531e 100644 --- a/src/util/virrandom.c +++ b/src/util/virrandom.c @@ -68,7 +68,9 @@ uint64_t virRandomBits(int nbits) return 0; } - ret &= (1ULL << nbits) - 1; + if (nbits < 64) + ret &= (1ULL << nbits) - 1; + return ret; } -- 2.16.4
On Thu, Aug 02, 2018 at 09:35:49AM +0200, Michal Privoznik wrote:
If nbits is 64 (or greater) then shifting 1ULL left is undefined.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/util/virrandom.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/src/util/virrandom.c b/src/util/virrandom.c index 3c011a8615..7915f6531e 100644 --- a/src/util/virrandom.c +++ b/src/util/virrandom.c @@ -68,7 +68,9 @@ uint64_t virRandomBits(int nbits) return 0; }
- ret &= (1ULL << nbits) - 1; + if (nbits < 64) + ret &= (1ULL << nbits) - 1; + return ret; }
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
participants (2)
-
Daniel P. Berrangé -
Michal Privoznik