CVE-2023-53790

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

bpf: Zeroing allocated object from slab in bpf memory allocator

Currently the freed element in bpf memory allocator may be immediately

reused, for htab map the reuse will reinitialize special fields in map

value (e.g., bpf_spin_lock), but lookup procedure may still access

these special fields, and it may lead to hard-lockup as shown below:

NMI backtrace for cpu 16

CPU: 16 PID: 2574 Comm: htab.bin Tainted: G L 6.1.0+ #1

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),

RIP: 0010:queued_spin_lock_slowpath+0x283/0x2c0

......

Call Trace:

<TASK>

copy_map_value_locked+0xb7/0x170

bpf_map_copy_value+0x113/0x3c0

__sys_bpf+0x1c67/0x2780

__x64_sys_bpf+0x1c/0x20

do_syscall_64+0x30/0x60

entry_SYSCALL_64_after_hwframe+0x46/0xb0

......

</TASK>

For htab map, just like the preallocated case, these is no need to

initialize these special fields in map value again once these fields

have been initialized. For preallocated htab map, these fields are

initialized through __GFP_ZERO in bpf_map_area_alloc(), so do the

similar thing for non-preallocated htab in bpf memory allocator. And

there is no need to use __GFP_ZERO for per-cpu bpf memory allocator,

because __alloc_percpu_gfp() does it implicitly.