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cleanerd: cap segments per clean to prevent size_t overflow

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In nilfs_xreclaim_segment(), the total number of reclaimable blocks is
calculated as:

    (blocks_per_segment * nsegs) - ...

On 32-bit systems, where 'size_t' is 32-bit, this multiplication can
theoretically overflow if the total number of blocks exceeds
'SIZE_MAX'.

To prevent this, calculate a safe maximum number of segments per
cleaning step ('max_nsegs_per_step') at initialization based on the
volume's layout information (blocks per segment).  Apply this cap
whenever the cleaning speed is configured, ensuring the total block
count always fits within 'size_t'.

Also, add a sanity check for zero 'blocks_per_segment' during
initialization.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
This commit is contained in:
Ryusuke Konishi 2026-01-24 12:59:59 +09:00
parent 2cab9d90f7
commit 4a733f7ff0
1 changed files with 26 additions and 3 deletions
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29
sbin/cleanerd.c
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@ -136,6 +136,8 @@ static const struct option long_option[] = {
* @no_timeout: the next timeout will be 0 seconds
* @shutdown: shutdown request flag
* @nsegs_per_step: number of segments cleaned per cleaning step
* @max_nsegs_per_step: upper limit of the number of segments cleaned per
* cleaning step
* @cleaning_interval: cleaning interval
* @target: target time for sleeping (monotonic time)
* @timeout: timeout value for sleeping
@ -171,6 +173,7 @@ struct nilfs_cleanerd {
bool shutdown : 1;
unsigned int nsegs_per_step;
unsigned int max_nsegs_per_step;
struct timespec cleaning_interval;
struct timespec target;
struct timespec timeout;
@ -259,6 +262,8 @@ skip_monotonic_clock:
syslog(LOG_DEBUG, "no_timeout: %d", cleanerd->no_timeout);
syslog(LOG_DEBUG, "shutdown: %d", cleanerd->shutdown);
syslog(LOG_DEBUG, "nsegs_per_step: %u", cleanerd->nsegs_per_step);
syslog(LOG_DEBUG, "max_nsegs_per_step: %u",
cleanerd->max_nsegs_per_step);
syslog(LOG_DEBUG, "cleaning_interval: %ld.%09ld",
cleanerd->cleaning_interval.tv_sec,
cleanerd->cleaning_interval.tv_nsec);
@ -352,7 +357,9 @@ static int nilfs_cleanerd_reconfig(struct nilfs_cleanerd *cleanerd,
if (unlikely(ret < 0)) {
syslog(LOG_ERR, "cannot configure: %m");
} else {
cleanerd->nsegs_per_step = config->cf_nsegments_per_clean;
cleanerd->nsegs_per_step = min_t(
unsigned int, config->cf_nsegments_per_clean,
cleanerd->max_nsegs_per_step);
cleanerd->cleaning_interval = config->cf_cleaning_interval;
cleanerd->min_reclaimable_blocks =
config->cf_min_reclaimable_blocks;
@ -468,6 +475,7 @@ static struct nilfs_cleanerd *
nilfs_cleanerd_create(const char *dev, const char *dir, const char *conffile)
{
struct nilfs_cleanerd *cleanerd;
uint32_t blocks_per_segment;
int ret;
cleanerd = malloc(sizeof(*cleanerd));
@ -484,6 +492,17 @@ nilfs_cleanerd_create(const char *dev, const char *dir, const char *conffile)
goto out_cleanerd;
}
blocks_per_segment = nilfs_get_blocks_per_segment(cleanerd->nilfs);
if (unlikely(blocks_per_segment == 0)) {
syslog(LOG_ERR, "%s: invalid segment block count: 0", dev);
goto out_nilfs;
}
/* Calculate limit on segments per GC step. */
cleanerd->max_nsegs_per_step = min_t(
size_t, SIZE_MAX / blocks_per_segment,
NILFS_CLDCONFIG_NSEGMENTS_PER_CLEAN_MAX);
cleanerd->cnormap = nilfs_cnormap_create(cleanerd->nilfs);
if (unlikely(cleanerd->cnormap == NULL)) {
syslog(LOG_ERR,
@ -1161,7 +1180,9 @@ static int nilfs_cleanerd_cmd_run(struct nilfs_cleanerd *cleanerd,
req2->args.nsegments_per_clean >
NILFS_CLDCONFIG_NSEGMENTS_PER_CLEAN_MAX)
goto error_inval;
cleanerd->mm_nsegs_per_step = req2->args.nsegments_per_clean;
cleanerd->mm_nsegs_per_step = min_t(
unsigned int, req2->args.nsegments_per_clean,
cleanerd->max_nsegs_per_step);
} else {
cleanerd->mm_nsegs_per_step = cleanerd->nsegs_per_step;
}
@ -1685,7 +1706,9 @@ static int nilfs_cleanerd_clean_loop(struct nilfs_cleanerd *cleanerd)
if (unlikely(ret < 0))
return -1;
cleanerd->nsegs_per_step = cleanerd->config.cf_nsegments_per_clean;
cleanerd->nsegs_per_step = min_t(
unsigned int, cleanerd->config.cf_nsegments_per_clean,
cleanerd->max_nsegs_per_step);
cleanerd->cleaning_interval = cleanerd->config.cf_cleaning_interval;
cleanerd->min_reclaimable_blocks =
cleanerd->config.cf_min_reclaimable_blocks;