Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:LoongArch: Optimize module load time by optimizing PLT/GOT countingWhen enabling CONFIG_KASAN, CONFIG_PREEMPT_VOLUNTARY_BUILD andCONFIG_PREEMPT_VOLUNTARY at the same time, there will be soft deadlock,the relevant logs are as follows:rcu: INFO: rcu_sched self-detected stall on CPU...Call Trace:[<900000000024f9e4>] show_stack+0x5c/0x180[<90000000002482f4>] dump_stack_lvl+0x94/0xbc[<9000000000224544>] rcu_dump_cpu_stacks+0x1fc/0x280[<900000000037ac80>] rcu_sched_clock_irq+0x720/0xf88[<9000000000396c34>] update_process_times+0xb4/0x150[<90000000003b2474>] tick_nohz_handler+0xf4/0x250[<9000000000397e28>] __hrtimer_run_queues+0x1d0/0x428[<9000000000399b2c>] hrtimer_interrupt+0x214/0x538[<9000000000253634>] constant_timer_interrupt+0x64/0x80[<9000000000349938>] __handle_irq_event_percpu+0x78/0x1a0[<9000000000349a78>] handle_irq_event_percpu+0x18/0x88[<9000000000354c00>] handle_percpu_irq+0x90/0xf0[<9000000000348c74>] handle_irq_desc+0x94/0xb8[<9000000001012b28>] handle_cpu_irq+0x68/0xa0[<9000000001def8c0>] handle_loongarch_irq+0x30/0x48[<9000000001def958>] do_vint+0x80/0xd0[<9000000000268a0c>] kasan_mem_to_shadow.part.0+0x2c/0x2a0[<90000000006344f4>] __asan_load8+0x4c/0x120[<900000000025c0d0>] module_frob_arch_sections+0x5c8/0x6b8[<90000000003895f0>] load_module+0x9e0/0x2958[<900000000038b770>] __do_sys_init_module+0x208/0x2d0[<9000000001df0c34>] do_syscall+0x94/0x190[<900000000024d6fc>] handle_syscall+0xbc/0x158After analysis, this is because the slow speed of loading the amdgpumodule leads to the long time occupation of the cpu and then the softdeadlock.When loading a module, module_frob_arch_sections() tries to figure outthe number of PLTs/GOTs that will be needed to handle all the RELAs. Itwill call the count_max_entries() to find in an out-of-order date whichcounting algorithm has O(n^2) complexity.To make it faster, we sort the relocation list by info and addend. Thatway, to check for a duplicate relocation, it just needs to compare withthe previous entry. This reduces the complexity of the algorithm to O(n log n), as done in commit d4e0340919fb ("arm64/module: Optimize moduleload time by optimizing PLT counting"). This gives sinificant reductionin module load time for modules with large number of relocations.After applying this patch, the soft deadlock problem has been solved,and the kernel starts normally without "Call Trace".Using the default configuration to test some modules, the results are asfollows:Module Sizeip_tables 36Kfat 143Kradeon 2.5MBamdgpu 16MBWithout this patch:Module Module load time (ms) Count(PLTs/GOTs)ip_tables 18 59/6fat 0 162/14radeon 54 1221/84amdgpu 1411 4525/1098With this patch:Module Module load time (ms) Count(PLTs/GOTs)ip_tables 18 59/6fat 0 162/14radeon 22 1221/84amdgpu 45 4525/1098
No PoCs from references.
- https://github.com/w4zu/Debian_security