GHSA-VPCJ-FG84-6VGJ
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In the Linux kernel, the following vulnerability has been resolved:
usb: atm: usbatm: fix invalid ci_range initialization
syzbot reported a shift-out-of-bounds in __vcc_connect():
UBSAN: shift-out-of-bounds in net/atm/common.c:382:32 shift exponent -1 is negative CPU: 0 UID: 0 PID: 5987 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233 __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494 __vcc_connect+0x14b4/0x19c0 net/atm/common.c:382 vcc_connect+0x328/0x8f0 net/atm/common.c:498 pvc_bind+0x272/0x380 net/atm/pvc.c:52 __sys_bind+0x2e3/0x410 net/socket.c:1976 __x64_sys_bind+0x7a/0x90 net/socket.c:1979 ...
ATM device ci_range fields (vpi_bits and vci_bits) represent the number of bits supported for VPI and VCI addressing on the device. net/atm/common.c directly uses these fields as bit shift counts: vpi >> dev->ci_range.vpi_bits vci >> dev->ci_range.vci_bits 1 << vcc->dev->ci_range.vpi_bits 1 << vcc->dev->ci_range.vci_bits
usbatm_atm_init() sets ci_range.vpi_bits and ci_range.vci_bits to ATM_CI_MAX (-1), which is defined in as a sentinel value for userspace ATM_SETCIRANGE requests, not a valid bit count. Shifting by -1 is undefined behavior and triggers UBSAN warnings.
ATM UNI cell headers allow up to 8 bits for VPI (0..255) and 16 bits for VCI (0..65535). Initialize vpi_bits to 8 and vci_bits to 16, as done by solos-pci.
{
"affected": [],
"aliases": [
"CVE-2026-90055"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:16:54Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: atm: usbatm: fix invalid ci_range initialization\n\nsyzbot reported a shift-out-of-bounds in __vcc_connect():\n\n UBSAN: shift-out-of-bounds in net/atm/common.c:382:32\n shift exponent -1 is negative\n CPU: 0 UID: 0 PID: 5987 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)\n Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026\n Call Trace:\n \u003cTASK\u003e\n dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120\n ubsan_epilogue+0xa/0x30 lib/ubsan.c:233\n __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494\n __vcc_connect+0x14b4/0x19c0 net/atm/common.c:382\n vcc_connect+0x328/0x8f0 net/atm/common.c:498\n pvc_bind+0x272/0x380 net/atm/pvc.c:52\n __sys_bind+0x2e3/0x410 net/socket.c:1976\n __x64_sys_bind+0x7a/0x90 net/socket.c:1979\n ...\n\nATM device ci_range fields (vpi_bits and vci_bits) represent the\nnumber of bits supported for VPI and VCI addressing on the device.\nnet/atm/common.c directly uses these fields as bit shift counts:\n vpi \u003e\u003e dev-\u003eci_range.vpi_bits\n vci \u003e\u003e dev-\u003eci_range.vci_bits\n 1 \u003c\u003c vcc-\u003edev-\u003eci_range.vpi_bits\n 1 \u003c\u003c vcc-\u003edev-\u003eci_range.vci_bits\n\nusbatm_atm_init() sets ci_range.vpi_bits and ci_range.vci_bits to\nATM_CI_MAX (-1), which is defined in \u003cuapi/linux/atmdev.h\u003e as a\nsentinel value for userspace ATM_SETCIRANGE requests, not a valid bit\ncount. Shifting by -1 is undefined behavior and triggers UBSAN\nwarnings.\n\nATM UNI cell headers allow up to 8 bits for VPI (0..255) and 16 bits\nfor VCI (0..65535). Initialize vpi_bits to 8 and vci_bits to 16, as\ndone by solos-pci.",
"id": "GHSA-vpcj-fg84-6vgj",
"modified": "2026-09-17T18:31:48Z",
"published": "2026-09-17T18:31:48Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90055"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1e964d414bfd9f8dfe9948d08e4b9dda4ed2e422"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/561cbd6d49022c9a383e22a39c87a165a4d39f9c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/75667703115154a4fd9cf259d4f826d8729cbcda"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/76bc7c3a44856744b64aa91d9afe6d9522a78c42"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7baa0c92be39eb3da755ed6f200497a57078c47b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8442586526c406527bf31206e538c0ce6bc672e6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a60fd8c6dbaa76da4163cf225ed2b9e982540f39"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ff7f77a234f7b74e5955a6e34fa74eca4c9ca44c"
}
],
"schema_version": "1.4.0",
"severity": []
}
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