CVE-2024-38588

In the Linux kernel, the following vulnerability has been resolved:

ftrace: Fix possible use-after-free issue in ftrace_location()

KASAN reports a bug:

BUG: KASAN: use-after-free in ftrace_location+0x90/0x120 Read of size 8 at addr ffff888141d40010 by task insmod/424 CPU: 8 PID: 424 Comm: insmod Tainted: G W 6.9.0-rc2+ […] Call Trace: dump_stack_lvl+0x68/0xa0 print_report+0xcf/0x610 kasan_report+0xb5/0xe0 ftrace_location+0x90/0x120 register_kprobe+0x14b/0xa40 kprobe_init+0x2d/0xff0 [kprobe_example] do_one_initcall+0x8f/0x2d0 do_init_module+0x13a/0x3c0 load_module+0x3082/0x33d0 init_module_from_file+0xd2/0x130 __x64_sys_finit_module+0x306/0x440 do_syscall_64+0x68/0x140 entry_SYSCALL_64_after_hwframe+0x71/0x79

The root cause is that, in lookup_rec(), ftrace record of some address is being searched in ftrace pages of some module, but those ftrace pages at the same time is being freed in ftrace_release_mod() as the corresponding module is being deleted:

       CPU1                       |      CPU2

register_kprobes() { | delete_module() { check_kprobe_address_safe() { | arch_check_ftrace_location() { | ftrace_location() { | lookup_rec() // USE! | ftrace_release_mod() // Free!

To fix this issue:

1. Hold rcu lock as accessing ftrace pages in ftrace_location_range();
2. Use ftrace_location_range() instead of lookup_rec() in ftrace_location();
3. Call synchronize_rcu() before freeing any ftrace pages both in ftrace_process_locs()/ftrace_release_mod()/ftrace_free_mem().

Affected Software

References

• https://git.kernel.org/stable/c/31310e373f4c8c74e029d4326b283e757edabc0b
• https://git.kernel.org/stable/c/66df065b3106964e667b37bf8f7e55ec69d0c1f6
• https://git.kernel.org/stable/c/7b4881da5b19f65709f5c18c1a4d8caa2e496461
• https://git.kernel.org/stable/c/8ea8ef5e42173560ac510e92a1cc797ffeea8831
• https://git.kernel.org/stable/c/dbff5f0bfb2416b8b55c105ddbcd4f885e98fada
• https://git.kernel.org/stable/c/e60b613df8b6253def41215402f72986fee3fc8d