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runc: gracefully handle low RLIMIT_NOFILE instead of crashing #5097

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runc: gracefully handle low RLIMIT_NOFILE instead of crashing #5097

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a0014e3
libcontainer: prevent crash with low RLIMIT_NOFILE
arnavgogia20 Feb 2, 2026
caf1809
tests: add regression test for low RLIMIT_NOFILE (gh-5082)
arnavgogia20 Feb 2, 2026
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10 changes: 10 additions & 0 deletions libcontainer/init_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -613,6 +613,16 @@ func maybeClearRlimitNofileCache(limits []configs.Rlimit) {

func setupRlimits(limits []configs.Rlimit, pid int) error {
for _, rlimit := range limits {
// Enforce a minimum RLIMIT_NOFILE to prevent the Go runtime from crashing
// due to lack of file descriptors (e.g. for the network poller).
// See https://github.com/opencontainers/runc/issues/5082.
if rlimit.Type == unix.RLIMIT_NOFILE {
// 32 is a safe "minimum" (Go runtime + runc standard FDs).
// The issue report indicates <14 crashes.
if rlimit.Soft < 32 {
return fmt.Errorf("RLIMIT_NOFILE soft limit %d is too low, must be at least 32", rlimit.Soft)
}
}
if err := unix.Prlimit(pid, rlimit.Type, &unix.Rlimit{Max: rlimit.Hard, Cur: rlimit.Soft}, nil); err != nil {
return fmt.Errorf("error setting rlimit type %v: %w", rlimit.Type, err)
}
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13 changes: 13 additions & 0 deletions tests/integration/rlimits.bats
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Expand Up @@ -86,3 +86,16 @@ function exec_check_nofile() {
hard=$soft
exec_check_nofile "$soft" "$hard"
}

@test "runc run with low RLIMIT_NOFILE should error (gh-5082)" {
# Set a very low limit (10) which triggers the crash in the issue.
# We assert it fails with our nice error message.
update_config '.process.rlimits = [{"type": "RLIMIT_NOFILE", "soft": 10, "hard": 10}]'

runc run test_rlimit

# Expect failure
[ "$status" -ne 0 ]
# Expect our error message
[[ "$output" == *"RLIMIT_NOFILE soft limit 10 is too low"* ]]
}