Replace unsafe string functions with bounds-checked alternatives

[Copilot]

Multiple buffer overflow and integer overflow vulnerabilities exist in container initialization and cgroup management code due to unchecked string operations and arithmetic.

Changes

Buffer overflow fixes

• cgroup.c: Replaced 42 sprintf() calls with snprintf() in cgroup v1/v2 path construction
• chroot.c: Replaced 14 sprintf() and 3 strcpy()/strcat() calls in mount operations and QEMU binary handling
• mount.c, umount.c, rootless.c, unshare.c: Fixed 13 additional sprintf() calls in loop device paths, namespace files, and ID mapping

Integer overflow protection

• cgroup.c: Added overflow checks in memory_to_bytes() before KB/MB/GB multiplication
• Changed atoi() to atol() with LONG_MAX validation to prevent wraparound

Example

Before:

char memory_cgroup_path[PATH_MAX] = { '\0' };
sprintf(memory_cgroup_path, "/sys/fs/cgroup/memory/%d", container->container_id);

int megabytes = atoi(bytes);
sprintf(ret, "%d", megabytes * 1024 * 1024);

After:

char memory_cgroup_path[PATH_MAX] = { '\0' };
snprintf(memory_cgroup_path, sizeof(memory_cgroup_path), "/sys/fs/cgroup/memory/%d", container->container_id);

long megabytes = atol(bytes);
if (megabytes < 0 || megabytes > LONG_MAX / (1024 * 1024)) {
    ruri_error("Memory value out of range\n");
}
snprintf(ret, 1024, "%ld", megabytes * 1024 * 1024);

Total: 72 unsafe string operations eliminated across 6 files.

[!WARNING]

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Identify and suggest improvements to insecure code

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