CVE-2024-35886 in Linux
Riassunto
di VulDB • 19/06/2026
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This is a **kernel panic** (or at least a severe kernel oops) occurring in the Linux kernel, specifically within the **IPv6 forwarding information base (FIB)** code.
### Key Information from the Stack Trace
1. **Crash Location**: * `fib6_dump_done` in `net/ipv6/ip6_fib.c:570` (or 572). * This function is called when a netlink dump operation (used to query routing tables) is finished.
2. **Trigger**: * The workqueue `events` is executing `netlink_sock_destruct_work`. * This is triggered when a netlink socket is being destroyed (`netlink_sock_destruct` -> `__sk_destruct` -> `sk_free`). * Essentially, a netlink socket that was used to dump IPv6 routes is being freed, and during its cleanup, it calls `fib6_dump_done`.
3. **The Problem**: * The crash happens inside `fib6_dump_done`. * Looking at the code around `ip6_fib.c:570` in recent kernels (e.g., 5.15, 6.1, 6.6), `fib6_dump_done` typically does something like: ```c static int fib6_dump_done(struct netlink_dump_control *c) {
struct fib6_dump_ctx *ctx = container_of(c, struct fib6_dump_ctx, ctl); // ... fib6_table_flush(ctx->tb); // Or similar cleanup // ... } ``` * The most likely cause is a **use-after-free** or **null pointer dereference** on a structure that was already freed or corrupted. * The registers show `RAX=0`, which often indicates a null pointer dereference or a function returning 0 that was expected to be non-null. * The `CR2` register (`ffffc9000d97fff8`) is the faulting address. It looks like a stack address, which is unusual for a null deref but could indicate a corrupted pointer.
4. **Environment**: * **QEMU**: You are running in a QEMU virtual machine. * **BIOS**: `rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014` (old QEMU BIOS). * **Kernel**: The stack trace shows `net/ipv6/ip6_fib.c`, which is standard Linux kernel networking code.
### Likely Causes
1. **Race Condition in Netlink Dump**: * A netlink socket is being freed while a `fib6_dump` operation is still in progress or just finishing. * The `fib6_dump_ctx` structure might be freed prematurely, or the `fib6_table` it references is being modified concurrently.
2. **Bug in `fib6_dump_done`**: * There might be a bug in the kernel version you are using where `fib6_dump_done` accesses a pointer that is no longer valid. * This is a known class of bugs in Linux networking code, especially around netlink dump callbacks.
3. **Memory Corruption**: * General memory corruption in the kernel could lead to this.
### How to Debug/Fix
1. **Update Kernel**: * This bug might have been fixed in newer kernel versions. Check if there are known CVEs or bug reports for `fib6_dump_done` in your kernel version. * Try updating to a newer LTS kernel (e.g., 6.1, 6.6, or 6.12).
2. **Check for Known Bugs**: * Search for `fib6_dump_done kernel panic` or `fib6_dump_done netlink_sock_destruct` on kernel.org bugzilla or GitHub issues. * Example: [LWN.net](https://lwn.net/) or [Kernel Bugzilla](https://bugzilla.kernel.org/).
3. **Reproduce**: * Can you reproduce this by running `ip -6 route show` or similar commands? * Try to isolate the trigger. Is it related to specific routing table changes?
4. **Enable Debugging**: * Recompile the kernel with `CONFIG_DEBUG_INFO=y` and `CONFIG_KASAN=y` (Kernel Address Sanitizer) to get more detailed information about the memory corruption. * Add `loglevel=7` to kernel
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