# CVE-2025-38279: bpf: Do not include stack ptr register in precision backtracking bookkeeping

Status: published. Published: 2025-07-10. Updated: 2026-11-05.

In the Linux kernel, the following vulnerability has been resolved:

bpf: Do not include stack ptr register in precision backtracking bookkeeping

Yi Lai reported an issue ([1]) where the following warning appears
in kernel dmesg:
  [   60.643604] verifier backtracking bug
  [   60.643635] WARNING: CPU: 10 PID: 2315 at kernel/bpf/verifier.c:4302 __mark_chain_precision+0x3a6c/0x3e10
  [   60.648428] Modules linked in: bpf_testmod(OE)
  [   60.650471] CPU: 10 UID: 0 PID: 2315 Comm: test_progs Tainted: G           OE       6.15.0-rc4-gef11287f8289-dirty #327 PREEMPT(full)
  [   60.654385] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
  [   60.656682] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
  [   60.660475] RIP: 0010:__mark_chain_precision+0x3a6c/0x3e10
  [   60.662814] Code: 5a 30 84 89 ea e8 c4 d9 01 00 80 3d 3e 7d d8 04 00 0f 85 60 fa ff ff c6 05 31 7d d8 04
                       01 48 c7 c7 00 58 30 84 e8 c4 06 a5 ff <0f> 0b e9 46 fa ff ff 48 ...
  [   60.668720] RSP: 0018:ffff888116cc7298 EFLAGS: 00010246
  [   60.671075] RAX: 54d70e82dfd31900 RBX: ffff888115b65e20 RCX: 0000000000000000
  [   60.673659] RDX: 0000000000000001 RSI: 0000000000000004 RDI: 00000000ffffffff
  [   60.676241] RBP: 0000000000000400 R08: ffff8881f6f23bd3 R09: 1ffff1103ede477a
  [   60.678787] R10: dffffc0000000000 R11: ffffed103ede477b R12: ffff888115b60ae8
  [   60.681420] R13: 1ffff11022b6cbc4 R14: 00000000fffffff2 R15: 0000000000000001
  [   60.684030] FS:  00007fc2aedd80c0(0000) GS:ffff88826fa8a000(0000) knlGS:0000000000000000
  [   60.686837] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [   60.689027] CR2: 000056325369e000 CR3: 000000011088b002 CR4: 0000000000370ef0
  [   60.691623] Call Trace:
  [   60.692821]  <TASK>
  [   60.693960]  ? __pfx_verbose+0x10/0x10
  [   60.695656]  ? __pfx_disasm_kfunc_name+0x10/0x10
  [   60.697495]  check_cond_jmp_op+0x16f7/0x39b0
  [   60.699237]  do_check+0x58fa/0xab10
  ...

Further analysis shows the warning is at line 4302 as below:

  4294                 /* static subprog call instruction, which
  4295                  * means that we are exiting current subprog,
  4296                  * so only r1-r5 could be still requested as
  4297                  * precise, r0 and r6-r10 or any stack slot in
  4298                  * the current frame should be zero by now
  4299                  */
  4300                 if (bt_reg_mask(bt) & ~BPF_REGMASK_ARGS) {
  4301                         verbose(env, "BUG regs %x\n", bt_reg_mask(bt));
  4302                         WARN_ONCE(1, "verifier backtracking bug");
  4303                         return -EFAULT;
  4304                 }

With the below test (also in the next patch):
  __used __naked static void __bpf_jmp_r10(void)
  {
	asm volatile (
	"r2 = 2314885393468386424 ll;"
	"goto +0;"
	"if r2 <= r10 goto +3;"
	"if r1 >= -1835016 goto +0;"
	"if r2 <= 8 goto +0;"
	"if r3 <= 0 goto +0;"
	"exit;"
	::: __clobber_all);
  }

  SEC("?raw_tp")
  __naked void bpf_jmp_r10(void)
  {
	asm volatile (
	"r3 = 0 ll;"
	"call __bpf_jmp_r10;"
	"r0 = 0;"
	"exit;"
	::: __clobber_all);
  }

The following is the verifier failure log:
  0: (18) r3 = 0x0                      ; R3_w=0
  2: (85) call pc+2
  caller:
   R10=fp0
  callee:
   frame1: R1=ctx() R3_w=0 R10=fp0
  5: frame1: R1=ctx() R3_w=0 R10=fp0
  ; asm volatile ("                                 \ @ verifier_precision.c:184
  5: (18) r2 = 0x20202000256c6c78       ; frame1: R2_w=0x20202000256c6c78
  7: (05) goto pc+0
  8: (bd) if r2 <= r10 goto pc+3        ; frame1: R2_w=0x20202000256c6c78 R10=fp0
  9: (35) if r1 >= 0xffe3fff8 goto pc+0         ; frame1: R1=ctx()
  10: (b5) if r2 <= 0x8 goto pc+0
  mark_precise: frame1: last_idx 10 first_idx 0 subseq_idx -1
  mark_precise: frame1: regs=r2 stack= before 9: (35) if r1 >= 0xffe3fff8 goto pc+0
  mark_precise: frame1: regs=r2 stack= before 8: (bd) if r2 <= r10 goto pc+3
  mark_preci
---truncated---

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 407958a0e980b9e1842ab87b5a1040521e1e24e9; < 2d9a8022009d2d6ad7aaea249902d88f1fa70144 (affected, git); ≥ 407958a0e980b9e1842ab87b5a1040521e1e24e9; < 4265682c29c92f52c0da6fad5a79b5801462c8de (affected, git); ≥ 407958a0e980b9e1842ab87b5a1040521e1e24e9; < ac49b7560b4b08b1e4043a29214cc7ad77644c00 (affected, git); ≥ 407958a0e980b9e1842ab87b5a1040521e1e24e9; < e2d2115e56c4a02377189bfc3a9a7933552a7b0f (affected, git); fc2778c42f99c7de52fc004157b3c3ee4dcc208a (affected, git); ≥ 6.4.4; < 6.5 (affected, semver). Source: CNA: Linux
- Linux / Linux: 6.5 (affected); ≥ 0; < 6.5 (unaffected, semver); ≥ 6.6.160; ≤ 6.6.* (unaffected, semver); ≥ 6.12.37; ≤ 6.12.* (unaffected, semver); ≥ 6.15.3; ≤ 6.15.* (unaffected, semver); ≥ 6.16; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-05; percentile 14.71%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/2d9a8022009d2d6ad7aaea249902d88f1fa70144 (CNA: Linux)

- https://git.kernel.org/stable/c/4265682c29c92f52c0da6fad5a79b5801462c8de (CNA: Linux)

- https://git.kernel.org/stable/c/ac49b7560b4b08b1e4043a29214cc7ad77644c00 (CNA: Linux)

- https://git.kernel.org/stable/c/e2d2115e56c4a02377189bfc3a9a7933552a7b0f (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2025-38279; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2025-38279; retrieved 2026-11-05; source updated Not reported

Revision: 50f09492b437ecea98cc0dd286a71723ea6be565960e5fa750425b2fc2c8f1f6

Canonical: https://y2.dev/cve/CVE-2025-38279

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