CVE-2026-74411: wifi: rtw89: Correct data type for scan index to avoid infinite loop

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

wifi: rtw89: Correct data type for scan index to avoid infinite loop

A kernel soft lockup was observed during Wi-Fi scanning on the 6GHz band. The CPU becomes stuck in rtw89hwscanaddchanax for over 20 seconds, leading to a system panic.

RIP points to 0f b6 c3 (movzbl %bl, %eax), which zero-extends the low 8 bits of RBX into RAX. RBX (the counter i) has reached a huge value: 0x137466a1.

watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [kworker/u16:4:6124] Workqueue: eventsunbound cfg80211wiphywork [cfg80211] RIP: 0010:rtw89hwscanaddchanax+0xb3/0x6e0 [rtw89core] Code: a0 48 89 45 a8 44 89 6d 9c 44 89 75 98 eb 29 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 83 c3 01 <0f> b6 c3 41 3b 44 24 74 0f 83 0b 02 00 00 0f b6 c3 48 8d 14 80 49 RSP: 0018:ffffcb48cbaa39f8 EFLAGS: 00000202 RAX: 0000000000000005 RBX: 00000000137466a1 RCX: 0000000000000000 RDX: ffff89ffc9d851a8 RSI: 0000000000004f0d RDI: 0000000096af0130 RBP: ffffcb48cbaa3a60 R08: 0000000000000000 R09: ffff8a00b7502080 R10: ffff8a00b75ff600 R11: 0000000000000000 R12: ffff89ffc7553870 R13: ffff8a00b7ac8f19 R14: ffff8a00b75020d8 R15: ffff89ffc3d54d80 FS: 0000000000000000(0000) GS:ffff8a014f962000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007558d7f9f4c4 CR3: 0000000178040001 CR4: 00000000001706f0 Call Trace: <TASK> rtw89hwscanprepchanlistax+0x8a/0x400 [rtw89core] rtw89hwscanstart+0x546/0x8a0 [rtw89core] ? rtw89fwh2cdefaultcmactbl+0x13c/0x1f0 [rtw89core] rtw89opshwscan+0xae/0x120 [rtw89core] drvhwscan+0xbb/0x180 [mac80211] ieee80211startscan+0x2fc/0x750 [mac80211] ieee80211requestscan+0xe/0x20 [mac80211] ieee80211scan+0x123/0x190 [mac80211] rdevscan+0x40/0x110 [cfg80211] cfg80211scan6ghz+0x5a1/0xa30 [cfg80211]

By objdump with source:

for (i = 0; i < req->n6ghzparams; i++) { 5fbc0: 83 c3 01 add $0x1,%ebx --> i++ 5fbc3: 0f b6 c3 movzbl %bl,%eax --> get counter fbc6: 41 3b 44 24 74 cmp 0x74(%r12),%eax

RBX: 00000000137466a1 -> %bl = a1 -> EAX = 000000a1 (161)