GHSA-RW7C-WQQW-8W6C

Vulnerability from github – Published: 2024-02-22 18:30 – Updated: 2024-03-18 18:32
VLAI?
Details

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

bpf: Reject variable offset alu on PTR_TO_FLOW_KEYS

For PTR_TO_FLOW_KEYS, check_flow_keys_access() only uses fixed off for validation. However, variable offset ptr alu is not prohibited for this ptr kind. So the variable offset is not checked.

The following prog is accepted:

func#0 @0 0: R1=ctx() R10=fp0 0: (bf) r6 = r1 ; R1=ctx() R6_w=ctx() 1: (79) r7 = (u64 )(r6 +144) ; R6_w=ctx() R7_w=flow_keys() 2: (b7) r8 = 1024 ; R8_w=1024 3: (37) r8 /= 1 ; R8_w=scalar() 4: (57) r8 &= 1024 ; R8_w=scalar(smin=smin32=0, smax=umax=smax32=umax32=1024,var_off=(0x0; 0x400)) 5: (0f) r7 += r8 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r8 stack= before 4: (57) r8 &= 1024 mark_precise: frame0: regs=r8 stack= before 3: (37) r8 /= 1 mark_precise: frame0: regs=r8 stack= before 2: (b7) r8 = 1024 6: R7_w=flow_keys(smin=smin32=0,smax=umax=smax32=umax32=1024,var_off =(0x0; 0x400)) R8_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=1024, var_off=(0x0; 0x400)) 6: (79) r0 = (u64 )(r7 +0) ; R0_w=scalar() 7: (95) exit

This prog loads flow_keys to r7, and adds the variable offset r8 to r7, and finally causes out-of-bounds access:

BUG: unable to handle page fault for address: ffffc90014c80038 [...] Call Trace: bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline] __bpf_prog_run include/linux/filter.h:651 [inline] bpf_prog_run include/linux/filter.h:658 [inline] bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline] bpf_flow_dissect+0x15f/0x350 net/core/flow_dissector.c:991 bpf_prog_test_run_flow_dissector+0x39d/0x620 net/bpf/test_run.c:1359 bpf_prog_test_run kernel/bpf/syscall.c:4107 [inline] __sys_bpf+0xf8f/0x4560 kernel/bpf/syscall.c:5475 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline] __se_sys_bpf kernel/bpf/syscall.c:5559 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5559 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Fix this by rejecting ptr alu with variable offset on flow_keys. Applying the patch rejects the program with "R7 pointer arithmetic on flow_keys prohibited".

Severity ?
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2024-26589"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-119"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-02-22T17:15:09Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject variable offset alu on PTR_TO_FLOW_KEYS\n\nFor PTR_TO_FLOW_KEYS, check_flow_keys_access() only uses fixed off\nfor validation. However, variable offset ptr alu is not prohibited\nfor this ptr kind. So the variable offset is not checked.\n\nThe following prog is accepted:\n\n  func#0 @0\n  0: R1=ctx() R10=fp0\n  0: (bf) r6 = r1                       ; R1=ctx() R6_w=ctx()\n  1: (79) r7 = *(u64 *)(r6 +144)        ; R6_w=ctx() R7_w=flow_keys()\n  2: (b7) r8 = 1024                     ; R8_w=1024\n  3: (37) r8 /= 1                       ; R8_w=scalar()\n  4: (57) r8 \u0026= 1024                    ; R8_w=scalar(smin=smin32=0,\n  smax=umax=smax32=umax32=1024,var_off=(0x0; 0x400))\n  5: (0f) r7 += r8\n  mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1\n  mark_precise: frame0: regs=r8 stack= before 4: (57) r8 \u0026= 1024\n  mark_precise: frame0: regs=r8 stack= before 3: (37) r8 /= 1\n  mark_precise: frame0: regs=r8 stack= before 2: (b7) r8 = 1024\n  6: R7_w=flow_keys(smin=smin32=0,smax=umax=smax32=umax32=1024,var_off\n  =(0x0; 0x400)) R8_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=1024,\n  var_off=(0x0; 0x400))\n  6: (79) r0 = *(u64 *)(r7 +0)          ; R0_w=scalar()\n  7: (95) exit\n\nThis prog loads flow_keys to r7, and adds the variable offset r8\nto r7, and finally causes out-of-bounds access:\n\n  BUG: unable to handle page fault for address: ffffc90014c80038\n  [...]\n  Call Trace:\n   \u003cTASK\u003e\n   bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]\n   __bpf_prog_run include/linux/filter.h:651 [inline]\n   bpf_prog_run include/linux/filter.h:658 [inline]\n   bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]\n   bpf_flow_dissect+0x15f/0x350 net/core/flow_dissector.c:991\n   bpf_prog_test_run_flow_dissector+0x39d/0x620 net/bpf/test_run.c:1359\n   bpf_prog_test_run kernel/bpf/syscall.c:4107 [inline]\n   __sys_bpf+0xf8f/0x4560 kernel/bpf/syscall.c:5475\n   __do_sys_bpf kernel/bpf/syscall.c:5561 [inline]\n   __se_sys_bpf kernel/bpf/syscall.c:5559 [inline]\n   __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5559\n   do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n   do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:83\n   entry_SYSCALL_64_after_hwframe+0x63/0x6b\n\nFix this by rejecting ptr alu with variable offset on flow_keys.\nApplying the patch rejects the program with \"R7 pointer arithmetic\non flow_keys prohibited\".",
  "id": "GHSA-rw7c-wqqw-8w6c",
  "modified": "2024-03-18T18:32:18Z",
  "published": "2024-02-22T18:30:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26589"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1b500d5d6cecf98dd6ca88bc9e7ae1783c83e6d3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/22c7fa171a02d310e3a3f6ed46a698ca8a0060ed"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/29ffa63f21bcdcef3e36b03cccf9d0cd031f6ab0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4108b86e324da42f7ed425bd71632fd844300dc8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e8d3872b617c21100c5ee4f64e513997a68c2e3d"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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