GHSA-J93V-637X-3GWQ

Vulnerability from github – Published: 2025-07-04 15:31 – Updated: 2025-11-03 18:31
VLAI?
Details

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

fbdev: Fix fb_set_var to prevent null-ptr-deref in fb_videomode_to_var

If fb_add_videomode() in fb_set_var() fails to allocate memory for fb_videomode, later it may lead to a null-ptr dereference in fb_videomode_to_var(), as the fb_info is registered while not having the mode in modelist that is expected to be there, i.e. the one that is described in fb_info->var.

================================================================ general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 1 PID: 30371 Comm: syz-executor.1 Not tainted 5.10.226-syzkaller #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:fb_videomode_to_var+0x24/0x610 drivers/video/fbdev/core/modedb.c:901 Call Trace: display_to_var+0x3a/0x7c0 drivers/video/fbdev/core/fbcon.c:929 fbcon_resize+0x3e2/0x8f0 drivers/video/fbdev/core/fbcon.c:2071 resize_screen drivers/tty/vt/vt.c:1176 [inline] vc_do_resize+0x53a/0x1170 drivers/tty/vt/vt.c:1263 fbcon_modechanged+0x3ac/0x6e0 drivers/video/fbdev/core/fbcon.c:2720 fbcon_update_vcs+0x43/0x60 drivers/video/fbdev/core/fbcon.c:2776 do_fb_ioctl+0x6d2/0x740 drivers/video/fbdev/core/fbmem.c:1128 fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1203 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:739 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x67/0xd1 ================================================================

The reason is that fb_info->var is being modified in fb_set_var(), and then fb_videomode_to_var() is called. If it fails to add the mode to fb_info->modelist, fb_set_var() returns error, but does not restore the old value of fb_info->var. Restore fb_info->var on failure the same way it is done earlier in the function.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

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{
  "affected": [],
  "aliases": [
    "CVE-2025-38214"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-07-04T14:15:29Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: Fix fb_set_var to prevent null-ptr-deref in fb_videomode_to_var\n\nIf fb_add_videomode() in fb_set_var() fails to allocate memory for\nfb_videomode, later it may lead to a null-ptr dereference in\nfb_videomode_to_var(), as the fb_info is registered while not having the\nmode in modelist that is expected to be there, i.e. the one that is\ndescribed in fb_info-\u003evar.\n\n================================================================\ngeneral protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI\nKASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]\nCPU: 1 PID: 30371 Comm: syz-executor.1 Not tainted 5.10.226-syzkaller #0\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014\nRIP: 0010:fb_videomode_to_var+0x24/0x610 drivers/video/fbdev/core/modedb.c:901\nCall Trace:\n display_to_var+0x3a/0x7c0 drivers/video/fbdev/core/fbcon.c:929\n fbcon_resize+0x3e2/0x8f0 drivers/video/fbdev/core/fbcon.c:2071\n resize_screen drivers/tty/vt/vt.c:1176 [inline]\n vc_do_resize+0x53a/0x1170 drivers/tty/vt/vt.c:1263\n fbcon_modechanged+0x3ac/0x6e0 drivers/video/fbdev/core/fbcon.c:2720\n fbcon_update_vcs+0x43/0x60 drivers/video/fbdev/core/fbcon.c:2776\n do_fb_ioctl+0x6d2/0x740 drivers/video/fbdev/core/fbmem.c:1128\n fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1203\n vfs_ioctl fs/ioctl.c:48 [inline]\n __do_sys_ioctl fs/ioctl.c:753 [inline]\n __se_sys_ioctl fs/ioctl.c:739 [inline]\n __x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:739\n do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46\n entry_SYSCALL_64_after_hwframe+0x67/0xd1\n================================================================\n\nThe reason is that fb_info-\u003evar is being modified in fb_set_var(), and\nthen fb_videomode_to_var() is called. If it fails to add the mode to\nfb_info-\u003emodelist, fb_set_var() returns error, but does not restore the\nold value of fb_info-\u003evar. Restore fb_info-\u003evar on failure the same way\nit is done earlier in the function.\n\nFound by Linux Verification Center (linuxtesting.org) with Syzkaller.",
  "id": "GHSA-j93v-637x-3gwq",
  "modified": "2025-11-03T18:31:22Z",
  "published": "2025-07-04T15:31:09Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38214"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/05f6e183879d9785a3cdf2f08a498bc31b7a20aa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1a10d91766eb6ddfd5414e4785611e33a4fe0f9b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3ca78032a388a0795201792b36e6fc9b6e6e8eed"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8a3a2887794b2c8e78b3e5d6e3de724527c9f41b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b3071bb463ea1e6c686d0dc9638fc940f2f5cf17"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ee20216f12d9482cd70e44dae5e7fabb38367c71"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fab201d72fde38d081e2c5d4ad25595c535b7b22"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ff0e037241173b574b385bff53d67567b9816db5"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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Detection rules are retrieved from Rulezet.