Bug 2373540 (CVE-2022-49985)
| Summary: | CVE-2022-49985 kernel: bpf: Don't use tnum_range on array range checking for poke descriptors | ||
|---|---|---|---|
| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security DevOps Team <prodsec-dev> |
| Status: | NEW --- | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | unspecified | CC: | dfreiber, drow, jburrell, vkumar |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | --- | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
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: <TASK> 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.