jnd/beszel-ipv6
1
0
Fork 0
mirror of https://github.com/henrygd/beszel.git synced 2026-08-19 08:47:46 +02:00
Code Issues Packages Projects Releases 2 Wiki Activity

fix(agent): guard against unsigned underflow in memory calculations (closes #1978)

Browse Source 
Extract host memory derivation into calculateHostMemoryUsage and use
saturating subtraction to prevent uint64 underflow caused by race
conditions when reading /proc/meminfo. Also ensure UsedPercent guards
against division by zero.

Co-authored-by: Sven van Ginkel <svenvanginkel@icloud.com>
This commit is contained in:
henrygd
2026-08-13 17:06:10 -04:00
parent c9b6279e61
commit d40372842b
2 changed files with 94 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
agent/system.go
View File

@@ -169,21 +169,11 @@ func (a *Agent) getSystemStats(cacheTimeMs uint16) system.Stats {
// memory
if v, err := mem.VirtualMemory(); err == nil {
used, cacheBuff, swapUsed := calculateHostMemoryUsage(v, a.memCalc == "htop")
// swap
systemStats.Swap = utils.BytesToGigabytes(v.SwapTotal)
systemStats.SwapUsed = utils.BytesToGigabytes(v.SwapTotal - v.SwapFree - v.SwapCached)
// cache + buffers value for default mem calculation
// note: gopsutil automatically adds SReclaimable to v.Cached
cacheBuff := v.Cached + v.Buffers - v.Shared
if cacheBuff <= 0 {
cacheBuff = max(v.Total-v.Free-v.Used, 0)
}
// htop memory calculation overrides (likely outdated as of mid 2025)
if a.memCalc == "htop" {
// cacheBuff = v.Cached + v.Buffers - v.Shared
v.Used = v.Total - (v.Free + cacheBuff)
v.UsedPercent = float64(v.Used) / float64(v.Total) * 100.0
}
systemStats.SwapUsed = utils.BytesToGigabytes(swapUsed)
v.Used = used
// if a.memCalc == "legacy" {
// v.Used = v.Total - v.Free - v.Buffers - v.Cached
// cacheBuff = v.Total - v.Free - v.Used
@@ -193,10 +183,14 @@ func (a *Agent) getSystemStats(cacheTimeMs uint16) system.Stats {
if a.zfs {
if arcSize, _ := zfs.ARCSize(); arcSize > 0 && arcSize < v.Used {
v.Used = v.Used - arcSize
v.UsedPercent = float64(v.Used) / float64(v.Total) * 100.0
systemStats.MemZfsArc = utils.BytesToGigabytes(arcSize)
}
}
if v.Total > 0 {
v.UsedPercent = float64(v.Used) / float64(v.Total) * 100.0
} else {
v.UsedPercent = 0
}
systemStats.Mem = utils.BytesToGigabytes(v.Total)
systemStats.MemBuffCache = utils.BytesToGigabytes(cacheBuff)
systemStats.MemUsed = utils.BytesToGigabytes(v.Used)
@@ -263,6 +257,38 @@ func (a *Agent) getSystemStats(cacheTimeMs uint16) system.Stats {
return systemStats
}
// calculateHostMemoryUsage derives counters defensively because /proc/meminfo may
// change while gopsutil reads it. Invalid unsigned subtractions saturate at zero.
func calculateHostMemoryUsage(v *mem.VirtualMemoryStat, htop bool) (used, cacheBuff, swapUsed uint64) {
used = v.Used
if used > v.Total {
used = saturatingSub(v.Total, v.Available)
}
// gopsutil automatically adds SReclaimable to Cached.
cacheBuff = min(v.Cached, v.Total)
cacheBuff += min(v.Buffers, v.Total-cacheBuff)
cacheBuff = saturatingSub(cacheBuff, min(v.Shared, v.Total))
if v.Cached == 0 && v.Buffers == 0 {
cacheBuff = saturatingSub(v.Total, v.Free, used)
}
if htop {
used = saturatingSub(v.Total, v.Free, cacheBuff)
}
return used, cacheBuff, saturatingSub(v.SwapTotal, v.SwapFree, v.SwapCached)
}
// saturatingSub subtracts each value, returning zero on underflow.
func saturatingSub(value uint64, subtrahends ...uint64) uint64 {
for _, subtrahend := range subtrahends {
if subtrahend > value {
return 0
}
value -= subtrahend
}
return value
}
// getOsPrettyName attempts to get the pretty OS name from /etc/os-release on Linux systems
func getOsPrettyName() (string, error) {
file, err := os.Open("/etc/os-release")