CVE-2023-53441

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

bpf: cpumap: Fix memory leak in cpu_map_update_elem

Syzkaller reported a memory leak as follows:

BUG: memory leak unreferenced object 0xff110001198ef748 (size 192): comm syz-executor.3, pid 17672, jiffies 4298118891 (age 9.906s) hex dump (first 32 bytes): 00 00 00 00 4a 19 00 00 80 ad e3 e4 fe ff c0 00 ….J……….. 00 b2 d3 0c 01 00 11 ff 28 f5 8e 19 01 00 11 ff ……..(……. backtrace: [] __cpu_map_entry_alloc+0xf7/0xb00 [] cpu_map_update_elem+0x2fe/0x3d0 [] bpf_map_update_value.isra.0+0x2bd/0x520 [] map_update_elem+0x4cb/0x720 [] __se_sys_bpf+0x8c3/0xb90 [] do_syscall_64+0x30/0x40 [] entry_SYSCALL_64_after_hwframe+0x61/0xc6

BUG: memory leak unreferenced object 0xff110001198ef528 (size 192): comm syz-executor.3, pid 17672, jiffies 4298118891 (age 9.906s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. backtrace: [] __cpu_map_entry_alloc+0x260/0xb00 [] cpu_map_update_elem+0x2fe/0x3d0 [] bpf_map_update_value.isra.0+0x2bd/0x520 [] map_update_elem+0x4cb/0x720 [] __se_sys_bpf+0x8c3/0xb90 [] do_syscall_64+0x30/0x40 [] entry_SYSCALL_64_after_hwframe+0x61/0xc6

BUG: memory leak unreferenced object 0xff1100010fd93d68 (size 8): comm syz-executor.3, pid 17672, jiffies 4298118891 (age 9.906s) hex dump (first 8 bytes): 00 00 00 00 00 00 00 00 …….. backtrace: [] kvmalloc_node+0x11e/0x170 [] __cpu_map_entry_alloc+0x2f0/0xb00 [] cpu_map_update_elem+0x2fe/0x3d0 [] bpf_map_update_value.isra.0+0x2bd/0x520 [] map_update_elem+0x4cb/0x720 [] __se_sys_bpf+0x8c3/0xb90 [] do_syscall_64+0x30/0x40 [] entry_SYSCALL_64_after_hwframe+0x61/0xc6

In the cpu_map_update_elem flow, when kthread_stop is called before calling the threadfn of rcpu->kthread, since the KTHREAD_SHOULD_STOP bit of kthread has been set by kthread_stop, the threadfn of rcpu->kthread will never be executed, and rcpu->refcnt will never be 0, which will lead to the allocated rcpu, rcpu->queue and rcpu->queue->queue cannot be released.

Calling kthread_stop before executing kthreads threadfn will return -EINTR. We can complete the release of memory resources in this state.

Affected Software

References

• https://git.kernel.org/stable/c/4369016497319a9635702da010d02af1ebb1849d
• https://git.kernel.org/stable/c/a957ac8e0b5ffb5797382a6adbafd005a5f72851
• https://git.kernel.org/stable/c/b11a9b4f28cb6ff69ef7e69809e5f7fffeac9030
• https://git.kernel.org/stable/c/d26299f50f5ea8f0aeb5d49e659c31f64233c816