Summaryinfo

A vulnerability has been found in Linux Kernel up to 5.10.53/5.13.5 and classified as problematic. This vulnerability affects the function jit_subprogs of the component bpf. The manipulation leads to use after free. This vulnerability was named CVE-2021-47300. There is no exploit available. It is recommended to upgrade the affected component. Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Linux Kernel up to 5.10.53/5.13.5. This affects the function jit_subprogs of the component bpf. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. The impact remains unknown. The summary by CVE is:

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 ---truncated---

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2021-47300 since 05/21/2024. The exploitability is told to be difficult. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 12/26/2024).

Upgrading to version 5.10.54 or 5.13.6 eliminates this vulnerability. Applying the patch 39f1735c8107/cbb086074dab/5dd0a6b8582f is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.10.0
• 5.10.1
• 5.10.2
• 5.10.3
• 5.10.4
• 5.10.5
• 5.10.6
• 5.10.7
• 5.10.8
• 5.10.9
• 5.10.10
• 5.10.11
• 5.10.12
• 5.10.13
• 5.10.14
• 5.10.15
• 5.10.16
• 5.10.17
• 5.10.18
• 5.10.19
• 5.10.20
• 5.10.21
• 5.10.22
• 5.10.23
• 5.10.24
• 5.10.25
• 5.10.26
• 5.10.27
• 5.10.28
• 5.10.29
• 5.10.30
• 5.10.31
• 5.10.32
• 5.10.33
• 5.10.34
• 5.10.35
• 5.10.36
• 5.10.37
• 5.10.38
• 5.10.39
• 5.10.40
• 5.10.41
• 5.10.42
• 5.10.43
• 5.10.44
• 5.10.45
• 5.10.46
• 5.10.47
• 5.10.48
• 5.10.49
• 5.10.50
• 5.10.51
• 5.10.52
• 5.10.53
• 5.13.0
• 5.13.1
• 5.13.2
• 5.13.3
• 5.13.4
• 5.13.5

License

• open-source

CPE 2.3info

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CPE 2.2info

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