{"id":"AZL-64995","summary":"CVE-2025-38279 affecting package kernel 6.6.126.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Do not include stack ptr register in precision backtracking bookkeeping\n\nYi Lai reported an issue ([1]) where the following warning appears\nin kernel dmesg:\n  [   60.643604] verifier backtracking bug\n  [   60.643635] WARNING: CPU: 10 PID: 2315 at kernel/bpf/verifier.c:4302 __mark_chain_precision+0x3a6c/0x3e10\n  [   60.648428] Modules linked in: bpf_testmod(OE)\n  [   60.650471] CPU: 10 UID: 0 PID: 2315 Comm: test_progs Tainted: G           OE       6.15.0-rc4-gef11287f8289-dirty #327 PREEMPT(full)\n  [   60.654385] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE\n  [   60.656682] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014\n  [   60.660475] RIP: 0010:__mark_chain_precision+0x3a6c/0x3e10\n  [   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\n                       01 48 c7 c7 00 58 30 84 e8 c4 06 a5 ff \u003c0f\u003e 0b e9 46 fa ff ff 48 ...\n  [   60.668720] RSP: 0018:ffff888116cc7298 EFLAGS: 00010246\n  [   60.671075] RAX: 54d70e82dfd31900 RBX: ffff888115b65e20 RCX: 0000000000000000\n  [   60.673659] RDX: 0000000000000001 RSI: 0000000000000004 RDI: 00000000ffffffff\n  [   60.676241] RBP: 0000000000000400 R08: ffff8881f6f23bd3 R09: 1ffff1103ede477a\n  [   60.678787] R10: dffffc0000000000 R11: ffffed103ede477b R12: ffff888115b60ae8\n  [   60.681420] R13: 1ffff11022b6cbc4 R14: 00000000fffffff2 R15: 0000000000000001\n  [   60.684030] FS:  00007fc2aedd80c0(0000) GS:ffff88826fa8a000(0000) knlGS:0000000000000000\n  [   60.686837] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  [   60.689027] CR2: 000056325369e000 CR3: 000000011088b002 CR4: 0000000000370ef0\n  [   60.691623] Call Trace:\n  [   60.692821]  \u003cTASK\u003e\n  [   60.693960]  ? __pfx_verbose+0x10/0x10\n  [   60.695656]  ? __pfx_disasm_kfunc_name+0x10/0x10\n  [   60.697495]  check_cond_jmp_op+0x16f7/0x39b0\n  [   60.699237]  do_check+0x58fa/0xab10\n  ...\n\nFurther analysis shows the warning is at line 4302 as below:\n\n  4294                 /* static subprog call instruction, which\n  4295                  * means that we are exiting current subprog,\n  4296                  * so only r1-r5 could be still requested as\n  4297                  * precise, r0 and r6-r10 or any stack slot in\n  4298                  * the current frame should be zero by now\n  4299                  */\n  4300                 if (bt_reg_mask(bt) & ~BPF_REGMASK_ARGS) {\n  4301                         verbose(env, \"BUG regs %x\\n\", bt_reg_mask(bt));\n  4302                         WARN_ONCE(1, \"verifier backtracking bug\");\n  4303                         return -EFAULT;\n  4304                 }\n\nWith the below test (also in the next patch):\n  __used __naked static void __bpf_jmp_r10(void)\n  {\n\tasm volatile (\n\t\"r2 = 2314885393468386424 ll;\"\n\t\"goto +0;\"\n\t\"if r2 \u003c= r10 goto +3;\"\n\t\"if r1 \u003e= -1835016 goto +0;\"\n\t\"if r2 \u003c= 8 goto +0;\"\n\t\"if r3 \u003c= 0 goto +0;\"\n\t\"exit;\"\n\t::: __clobber_all);\n  }\n\n  SEC(\"?raw_tp\")\n  __naked void bpf_jmp_r10(void)\n  {\n\tasm volatile (\n\t\"r3 = 0 ll;\"\n\t\"call __bpf_jmp_r10;\"\n\t\"r0 = 0;\"\n\t\"exit;\"\n\t::: __clobber_all);\n  }\n\nThe following is the verifier failure log:\n  0: (18) r3 = 0x0                      ; R3_w=0\n  2: (85) call pc+2\n  caller:\n   R10=fp0\n  callee:\n   frame1: R1=ctx() R3_w=0 R10=fp0\n  5: frame1: R1=ctx() R3_w=0 R10=fp0\n  ; asm volatile (\"                                 \\ @ verifier_precision.c:184\n  5: (18) r2 = 0x20202000256c6c78       ; frame1: R2_w=0x20202000256c6c78\n  7: (05) goto pc+0\n  8: (bd) if r2 \u003c= r10 goto pc+3        ; frame1: R2_w=0x20202000256c6c78 R10=fp0\n  9: (35) if r1 \u003e= 0xffe3fff8 goto pc+0         ; frame1: R1=ctx()\n  10: (b5) if r2 \u003c= 0x8 goto pc+0\n  mark_precise: frame1: last_idx 10 first_idx 0 subseq_idx -1\n  mark_precise: frame1: regs=r2 stack= before 9: (35) if r1 \u003e= 0xffe3fff8 goto pc+0\n  mark_precise: frame1: regs=r2 stack= before 8: (bd) if r2 \u003c= r10 goto pc+3\n  mark_preci\n---truncated---","modified":"2026-04-01T05:20:27.478602Z","published":"2025-07-10T08:15:26Z","upstream":["CVE-2025-38279"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-38279"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.126.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-64995.json"}}],"schema_version":"1.7.5"}