CVE-2022-49985 Information

Jun 19, 2025 cve

Description

In the Linux kernel the following vulnerability has been resolved:

bpf: Don’t use tnum_range on array range checking for poke descriptors

Hsin-Wei reported a KASAN splat triggered by their BPF runtime fuzzer which is based on a customized syzkaller:

BUG: KASAN: slab-out-of-bounds in bpf_int_jit_compile+0x1257/0x13f0 Read of size 8 at addr ffff888004e90b58 by task syz-executor.0/1489 CPU: 1 PID: 1489 Comm: syz-executor.0 Not tainted 5.19.0 1 Hardware name: QEMU Standard PC (i440FX + PIIX 1996) BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: dump_stack_lvl+0x9c/0xc9 print_address_description.constprop.0+0x1f/0x1f0 ? bpf_int_jit_compile+0x1257/0x13f0 kasan_report.cold+0xeb/0x197 ? kvmalloc_node+0x170/0x200 ? bpf_int_jit_compile+0x1257/0x13f0 bpf_int_jit_compile+0x1257/0x13f0 ? arch_prepare_bpf_dispatcher+0xd0/0xd0 ? rcu_read_lock_sched_held+0x43/0x70 bpf_prog_select_runtime+0x3e8/0x640 ? bpf_obj_name_cpy+0x149/0x1b0 bpf_prog_load+0x102f/0x2220 ? __bpf_prog_put.constprop.0+0x220/0x220 ? find_held_lock+0x2c/0x110 ? __might_fault+0xd6/0x180 ? lock_downgrade+0x6e0/0x6e0 ? lock_is_held_type+0xa6/0x120 ? __might_fault+0x147/0x180 __sys_bpf+0x137b/0x6070 ? bpf_perf_link_attach+0x530/0x530 ? new_sync_read+0x600/0x600 ? __fget_files+0x255/0x450 ? lock_downgrade+0x6e0/0x6e0 ? fput+0x30/0x1a0 ? ksys_write+0x1a8/0x260 __x64_sys_bpf+0x7a/0xc0 ? syscall_enter_from_user_mode+0x21/0x70 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f917c4e2c2d

The problem here is that a range of tnum_range(0 map->max_entries - 1) has limited ability to represent the concrete tight range with the tnum as the set of resulting states from value + mask can result in a superset of the actual intended range and as such a tnum_in(range reg->var_off) check may yield true when it shouldn’t for example tnum_range(0 2) would result in 00XX -> v = 0000 m = 0011 such that the intended set of 0 1 2 is here represented by a less precise superset of 0 1 2 3. As the register is known const scalar really just use the concrete reg->var_off.value for the upper index check.

Reference

https://git.kernel.org/stable/c/4f672112f8665102a5842c170be1713f8ff95919 https://git.kernel.org/stable/c/a36df92c7ff7ecde2fb362241d0ab024dddd0597 https://git.kernel.org/stable/c/a657182a5c5150cdfacb6640aad1d2712571a409 https://git.kernel.org/stable/c/e8979807178434db8ceaa84dfcd44363e71e50bb

CNNVD-202506-2272 (Published: 2025-06-18)

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