| From bippy-7c5fe7eed585 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47300: bpf: Fix tail_call_reachable rejection for interpreter when jit failed |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| bpf: Fix tail_call_reachable rejection for interpreter when jit failed |
| |
| During testing of f263a81451c1 ("bpf: Track subprog poke descriptors correctly |
| and fix use-after-free") under various failure conditions, for example, when |
| jit_subprogs() fails and tries to clean up the program to be run under the |
| interpreter, we ran into the following freeze: |
| |
| [...] |
| #127/8 tailcall_bpf2bpf_3:FAIL |
| [...] |
| [ 92.041251] BUG: KASAN: slab-out-of-bounds in ___bpf_prog_run+0x1b9d/0x2e20 |
| [ 92.042408] Read of size 8 at addr ffff88800da67f68 by task test_progs/682 |
| [ 92.043707] |
| [ 92.044030] CPU: 1 PID: 682 Comm: test_progs Tainted: G O 5.13.0-53301-ge6c08cb33a30-dirty #87 |
| [ 92.045542] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014 |
| [ 92.046785] Call Trace: |
| [ 92.047171] ? __bpf_prog_run_args64+0xc0/0xc0 |
| [ 92.047773] ? __bpf_prog_run_args32+0x8b/0xb0 |
| [ 92.048389] ? __bpf_prog_run_args64+0xc0/0xc0 |
| [ 92.049019] ? ktime_get+0x117/0x130 |
| [...] // few hundred [similar] lines more |
| [ 92.659025] ? ktime_get+0x117/0x130 |
| [ 92.659845] ? __bpf_prog_run_args64+0xc0/0xc0 |
| [ 92.660738] ? __bpf_prog_run_args32+0x8b/0xb0 |
| [ 92.661528] ? __bpf_prog_run_args64+0xc0/0xc0 |
| [ 92.662378] ? print_usage_bug+0x50/0x50 |
| [ 92.663221] ? print_usage_bug+0x50/0x50 |
| [ 92.664077] ? bpf_ksym_find+0x9c/0xe0 |
| [ 92.664887] ? ktime_get+0x117/0x130 |
| [ 92.665624] ? kernel_text_address+0xf5/0x100 |
| [ 92.666529] ? __kernel_text_address+0xe/0x30 |
| [ 92.667725] ? unwind_get_return_address+0x2f/0x50 |
| [ 92.668854] ? ___bpf_prog_run+0x15d4/0x2e20 |
| [ 92.670185] ? ktime_get+0x117/0x130 |
| [ 92.671130] ? __bpf_prog_run_args64+0xc0/0xc0 |
| [ 92.672020] ? __bpf_prog_run_args32+0x8b/0xb0 |
| [ 92.672860] ? __bpf_prog_run_args64+0xc0/0xc0 |
| [ 92.675159] ? ktime_get+0x117/0x130 |
| [ 92.677074] ? lock_is_held_type+0xd5/0x130 |
| [ 92.678662] ? ___bpf_prog_run+0x15d4/0x2e20 |
| [ 92.680046] ? ktime_get+0x117/0x130 |
| [ 92.681285] ? __bpf_prog_run32+0x6b/0x90 |
| [ 92.682601] ? __bpf_prog_run64+0x90/0x90 |
| [ 92.683636] ? lock_downgrade+0x370/0x370 |
| [ 92.684647] ? mark_held_locks+0x44/0x90 |
| [ 92.685652] ? ktime_get+0x117/0x130 |
| [ 92.686752] ? lockdep_hardirqs_on+0x79/0x100 |
| [ 92.688004] ? ktime_get+0x117/0x130 |
| [ 92.688573] ? __cant_migrate+0x2b/0x80 |
| [ 92.689192] ? bpf_test_run+0x2f4/0x510 |
| [ 92.689869] ? bpf_test_timer_continue+0x1c0/0x1c0 |
| [ 92.690856] ? rcu_read_lock_bh_held+0x90/0x90 |
| [ 92.691506] ? __kasan_slab_alloc+0x61/0x80 |
| [ 92.692128] ? eth_type_trans+0x128/0x240 |
| [ 92.692737] ? __build_skb+0x46/0x50 |
| [ 92.693252] ? bpf_prog_test_run_skb+0x65e/0xc50 |
| [ 92.693954] ? bpf_prog_test_run_raw_tp+0x2d0/0x2d0 |
| [ 92.694639] ? __fget_light+0xa1/0x100 |
| [ 92.695162] ? bpf_prog_inc+0x23/0x30 |
| [ 92.695685] ? __sys_bpf+0xb40/0x2c80 |
| [ 92.696324] ? bpf_link_get_from_fd+0x90/0x90 |
| [ 92.697150] ? mark_held_locks+0x24/0x90 |
| [ 92.698007] ? lockdep_hardirqs_on_prepare+0x124/0x220 |
| [ 92.699045] ? finish_task_switch+0xe6/0x370 |
| [ 92.700072] ? lockdep_hardirqs_on+0x79/0x100 |
| [ 92.701233] ? finish_task_switch+0x11d/0x370 |
| [ 92.702264] ? __switch_to+0x2c0/0x740 |
| [ 92.703148] ? mark_held_locks+0x24/0x90 |
| [ 92.704155] ? __x64_sys_bpf+0x45/0x50 |
| [ 92.705146] ? do_syscall_64+0x35/0x80 |
| [ 92.706953] ? entry_SYSCALL_64_after_hwframe+0x44/0xae |
| [...] |
| |
| Turns out that the program rejection from e411901c0b77 ("bpf: allow for tailcalls |
| in BPF subprograms for x64 JIT") is buggy since env->prog->aux->tail_call_reachable |
| is never true. Commit ebf7d1f508a7 ("bpf, x64: rework pro/epilogue and tailcall |
| handling in JIT") added a tracker into check_max_stack_depth() which propagates |
| the tail_call_reachable condition throughout the subprograms. This info is then |
| assigned to the subprogram's func[i]->aux->tail_call_reachable. However, in the |
| case of the rejection check upon JIT failure, env->prog->aux->tail_call_reachable |
| is used. func[0]->aux->tail_call_reachable which represents the main program's |
| information did not propagate this to the outer env->prog->aux, though. Add this |
| propagation into check_max_stack_depth() where it needs to belong so that the |
| check can be done reliably. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47300 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.10 with commit ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 and fixed in 5.10.54 with commit 39f1735c8107ef43a53c4daf82f330d880488d8f |
| Issue introduced in 5.10 with commit ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 and fixed in 5.13.6 with commit cbb086074dab631ac43f8645cbac1d7b148e05c4 |
| Issue introduced in 5.10 with commit ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 and fixed in 5.14 with commit 5dd0a6b8582ffbfa88351949d50eccd5b6694ade |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47300 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| kernel/bpf/verifier.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/39f1735c8107ef43a53c4daf82f330d880488d8f |
| https://git.kernel.org/stable/c/cbb086074dab631ac43f8645cbac1d7b148e05c4 |
| https://git.kernel.org/stable/c/5dd0a6b8582ffbfa88351949d50eccd5b6694ade |
