| Message ID | 1b2e3049803f71cafb2e1fa1be4fb47147a0d398.1503580370.git.berto@igalia.com |
|---|---|
| State | New |
| Headers | show |
On 08/24/2017 08:24 AM, Alberto Garcia wrote: > LeakyBucket.burst_length is defined as an unsigned integer but the > code never checks for overflows and it only makes sure that the value > is not 0. > > In practice this means that the user can set something like > throttling.iops-total-max-length=4294967300 despite being larger than > UINT_MAX and the final value after casting to unsigned int will be 4. > > This patch changes the data type to uint64_t. This does not increase > the storage size of LeakyBucket, and allows us to assign the value > directly from qemu_opt_get_number() or BlockIOThrottle and then do the > checks directly in throttle_is_valid(). > > The value of burst_length does not have a specific upper limit, > but since the bucket size is defined by max * burst_length we have > to prevent overflows. Instead of going for UINT64_MAX or something > similar this patch reuses THROTTLE_VALUE_MAX, which allows I/O bursts > of 1 GiB/s for 10 days in a row. > > Signed-off-by: Alberto Garcia <berto@igalia.com> > --- > include/qemu/throttle.h | 2 +- > util/throttle.c | 5 +++++ > 2 files changed, 6 insertions(+), 1 deletion(-) > Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/include/qemu/throttle.h b/include/qemu/throttle.h index 6e31155fd4..8e01885d29 100644 --- a/include/qemu/throttle.h +++ b/include/qemu/throttle.h @@ -81,7 +81,7 @@ typedef struct LeakyBucket { uint64_t max; /* leaky bucket max burst in units */ double level; /* bucket level in units */ double burst_level; /* bucket level in units (for computing bursts) */ - unsigned burst_length; /* max length of the burst period, in seconds */ + uint64_t burst_length; /* max length of the burst period, in seconds */ } LeakyBucket; /* The following structure is used to configure a ThrottleState diff --git a/util/throttle.c b/util/throttle.c index 80660ffd2c..b8c524336c 100644 --- a/util/throttle.c +++ b/util/throttle.c @@ -354,6 +354,11 @@ bool throttle_is_valid(ThrottleConfig *cfg, Error **errp) return false; } + if (bkt->max && bkt->burst_length > THROTTLE_VALUE_MAX / bkt->max) { + error_setg(errp, "burst length too high for this burst rate"); + return false; + } + if (bkt->max && !bkt->avg) { error_setg(errp, "bps_max/iops_max require corresponding" " bps/iops values");
LeakyBucket.burst_length is defined as an unsigned integer but the code never checks for overflows and it only makes sure that the value is not 0. In practice this means that the user can set something like throttling.iops-total-max-length=4294967300 despite being larger than UINT_MAX and the final value after casting to unsigned int will be 4. This patch changes the data type to uint64_t. This does not increase the storage size of LeakyBucket, and allows us to assign the value directly from qemu_opt_get_number() or BlockIOThrottle and then do the checks directly in throttle_is_valid(). The value of burst_length does not have a specific upper limit, but since the bucket size is defined by max * burst_length we have to prevent overflows. Instead of going for UINT64_MAX or something similar this patch reuses THROTTLE_VALUE_MAX, which allows I/O bursts of 1 GiB/s for 10 days in a row. Signed-off-by: Alberto Garcia <berto@igalia.com> --- include/qemu/throttle.h | 2 +- util/throttle.c | 5 +++++ 2 files changed, 6 insertions(+), 1 deletion(-)