CVE-2025-39767

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

LoongArch: Optimize module load time by optimizing PLT/GOT counting

When enabling CONFIG_KASAN, CONFIG_PREEMPT_VOLUNTARY_BUILD and
CONFIG_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:
[] show_stack+0x5c/0x180
[] dump_stack_lvl+0x94/0xbc
[] rcu_dump_cpu_stacks+0x1fc/0x280
[] rcu_sched_clock_irq+0x720/0xf88
[] update_process_times+0xb4/0x150
[] tick_nohz_handler+0xf4/0x250
[] __hrtimer_run_queues+0x1d0/0x428
[] hrtimer_interrupt+0x214/0x538
[] constant_timer_interrupt+0x64/0x80
[] __handle_irq_event_percpu+0x78/0x1a0
[] handle_irq_event_percpu+0x18/0x88
[] handle_percpu_irq+0x90/0xf0
[] handle_irq_desc+0x94/0xb8
[] handle_cpu_irq+0x68/0xa0
[] handle_loongarch_irq+0x30/0x48
[] do_vint+0x80/0xd0
[] kasan_mem_to_shadow.part.0+0x2c/0x2a0
[] __asan_load8+0x4c/0x120
[] module_frob_arch_sections+0x5c8/0x6b8
[] load_module+0x9e0/0x2958
[] __do_sys_init_module+0x208/0x2d0
[] do_syscall+0x94/0x190
[] handle_syscall+0xbc/0x158

After analysis, this is because the slow speed of loading the amdgpu
module leads to the long time occupation of the cpu and then the soft
deadlock.

When loading a module, module_frob_arch_sections() tries to figure out
the number of PLTs/GOTs that will be needed to handle all the RELAs. It
will call the count_max_entries() to find in an out-of-order date which
counting algorithm has O(n^2) complexity.

To make it faster, we sort the relocation list by info and addend. That
way, to check for a duplicate relocation, it just needs to compare with
the previous entry. This reduces the complexity of the algorithm to O(n
log n), as done in commit d4e0340919fb (“arm64/module: Optimize module
load time by optimizing PLT counting”). This gives sinificant reduction
in 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 as
follows:

Module Size
ip_tables 36K
fat 143K
radeon 2.5MB
amdgpu 16MB

Without this patch:
Module Module load time (ms) Count(PLTs/GOTs)
ip_tables 18 59/6
fat 0 162/14
radeon 54 1221/84
amdgpu 1411 4525/1098

With this patch:
Module Module load time (ms) Count(PLTs/GOTs)
ip_tables 18 59/6
fat 0 162/14
radeon 22 1221/84
amdgpu 45 4525/1098