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TI-2021-21958 Aliases CVE-2021-47300GHSA-w5h4-c4xx-3r8p

bpf: Fix tail_call_reachable rejection for interpreter when jit failed

Priority LOW 34CWE-125Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 2 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

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---

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00237 14th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.10.54, 5.13.6, 5.14Red Hat: 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.10 and later5.10.54, 5.13.6, 5.14Patch availableCNA
  • Linux VendorLinux Affected 5.10 and later Fixed in 5.10.54, 5.13.6, 5.14 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*5.10 to before 5.10.54; 5.11 to before 5.13.6VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.14:rc1:*:*:*:*:*:*5.14 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.14:rc2:*:*:*:*:*:*5.14 rc2VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.10 to before 5.10.54; 5.11 to before 5.13.6 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.14:rc1:*:*:*:*:*:* Versions 5.14 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.14:rc2:*:*:*:*:*:* Versions 5.14 rc2 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.10.54, 5.13.6, 5.14

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 8AffectedNo fix planned: Will not fix
Not affected: 3 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47300
  2. 2026-10-03 Alias added: GHSA-w5h4-c4xx-3r8p

References

Patch 3

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences