Inspektor Gadget: Unprivileged container can crash USDT note parser via crafted ELF (no shipped gadget affected)

Description

## Summary A malicious container can crash or destabilize the privileged Inspektor Gadget process when a **gadget using USDT probes** is deployed. The vulnerability is in the USDT note parser (`pkg/uprobetracer/usdt.go`) which is invoked when a gadget with a `SEC("usdt/...")` section attaches to a target binary. An unprivileged process can place a crafted ELF binary at the expected library path, triggering one of two attack vectors: 1. **Panic (immediate crash):** A stapsdt note with a small `DescSize` causes an out-of-bounds slice access, panicking the IG process. 2. **Memory exhaustion (OOM kill):** A stapsdt note with a very large `NameSize` or `DescSize` causes IG to allocate up to ~4 GiB of memory, which can killnthe process if deployed with memory restrictions (e.g., cgroup limits). **Important:** The vulnerability is only triggered when running a gadget that uses USDT probes (i.e., contains a `SEC("usdt/...")` eBPF section). No gadget shipped by the Inspektor Gadget project uses USDT today. Users who deploy their own custom USDT gadgets are affected. ## Severity **Low** — Denial of Service (process crash or OOM) of a privileged host process, triggered by an unprivileged container. The vulnerable code path is only reached when a gadget using USDT probes is deployed. No such gadget is shipped by the Inspektor Gadget project; only users running custom USDT gadgets are affected. - **Attack vector**: An unprivileged process in a container places a crafted ELF file at a path that a USDT gadget targets (e.g., a library name resolved via the container's ld cache). When the gadget attaches, IG parses the malicious ELF and crashes. - **Impact**: The IG process panics and crashes (vector 1) or is OOM-killed (vector 2). This is a DoS against the monitoring infrastructure, not a code execution or privilege escalation vulnerability. - **Affected component**: `pkg/uprobetracer/usdt.go`, function `getUsdtInfo()` - **Prerequisites**: A gadget with a `SEC("usdt/...")` eBPF section must be running and configured to attach to a library inside the attacker's container. **No shipped gadgets use USDT probes**, so this only affects deployments with custom USDT gadgets. ## Affected Versions All versions of Inspektor Gadget that include USDT support in `pkg/uprobetracer/usdt.go`, starting from v0.28.0 (commit 7ee5e7a90 "pkg/uprobetracer: support USDT trace points"). ## Root Cause ### Vector 1: Out-of-bounds slice access (panic) In `pkg/uprobetracer/usdt.go`, the function `getUsdtInfo()` parses stapsdt notes from an ELF file's `.note.stapsdt` section. When a matching note is found (`name == "stapsdt\0"` and `type == 3`), it reads three address fields from the note descriptor: ```go // usdt.go lines 137-139 elfLocation := elfReader.ByteOrder.Uint64(desc[:wordSize]) elfBase := elfReader.ByteOrder.Uint64(desc[wordSize : 2*wordSize]) elfSemaphore := elfReader.ByteOrder.Uint64(desc[2*wordSize : 3*wordSize]) ``` For a 64-bit ELF, `wordSize = 8`, so this requires `desc` to be at least 24 bytes. However, `desc` is allocated based on the note's `DescSize` field from the ELF file: ```go desc := make([]byte, alignUp(uint64(header.DescSize), 4)) ``` A crafted ELF with `DescSize = 1` produces a 4-byte `desc` buffer. The expression `desc[:8]` then panics with: ``` panic: runtime error: slice bounds out of range [:8] with capacity 4 ``` ### Vector 2: Unbounded memory allocation (OOM) The `NameSize` and `DescSize` fields from the note header are used directly to allocate memory without any upper bound: ```go name := make([]byte, alignUp(uint64(header.NameSize), 4)) desc := make([]byte, alignUp(uint64(header.DescSize), 4)) ``` A crafted ELF with `NameSize = 0xFFFFFFFF` would attempt to allocate ~4 GiB of memory. Under cgroup memory limits (common in Kubernetes deployments), this triggers an OOM kill of the IG process. ### Vector 3: Missing panic recovery for `debug/elf` Go's `debug/elf` package is [not hardened against adversarial inputs](https://github.com/golang/go/issuesq=is%3Aissue+is%3Aopen+debug%2Felf+in%3Atitle) and may panic on malformed ELF headers. The cilium/ebpf library addresses this with its [`SafeELFFile` wrapper](https://github.com/cilium/ebpf/blob/main/internal/safeelf.go) that uses `recover()`, but `getUsdtInfo()` calls `elf.NewFile()` directly without any panic recovery. ## Fix The fix (3 changes in `pkg/uprobetracer/usdt.go`): 1. **Bounds check on descriptor size**: Validate `len(desc) >= 3*wordSize` before accessing the address fields. Reject malformed notes with an error instead of panicking. 2. **Cap allocation sizes**: Limit `NameSize` and `DescSize` to a reasonable maximum (1 MiB) before allocating memory, preventing DoS via memory exhaustion. There is no standard upper bound for ELF note fields; 1 MiB is a generous arbitrary cap — legitimate USDT notes are typically under 1 KB. 3. **Panic recovery**: Wrap `getUsdtInfo()` with `defer/recover` to catch any panics from `debug/elf` on malformed input, converting them to errors. ## Related - Go `debug/elf` known issues: https://github.com/golang/go/issues?q=is%3Aissue+is%3Aopen+debug%2Felf+in%3Atitle - cilium/ebpf `SafeELFFile` wrapper: https://github.com/cilium/ebpf/blob/main/internal/safeelf.go — uses `recover()` around all `debug/elf` operations for exactly this reason.

Affected Packages (1)