CVE-2024-50227 — thunderbolt: Fix KASAN reported stack out-of-bounds read in tb_retimer_scan()

Affected: Linux

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

thunderbolt: Fix KASAN reported stack out-of-bounds read in tb_retimer_scan()

KASAN reported following issue:

BUG: KASAN: stack-out-of-bounds in tb_retimer_scan+0xffe/0x1550 [thunderbolt] Read of size 4 at addr ffff88810111fc1c by task kworker/u56:0/11 CPU: 0 UID: 0 PID: 11 Comm: kworker/u56:0 Tainted: G U 6.11.0+ #1387 Tainted: [U]=USER Workqueue: thunderbolt0 tb_handle_hotplug [thunderbolt] Call Trace: <TASK> dump_stack_lvl+0x6c/0x90 print_report+0xd1/0x630 kasan_report+0xdb/0x110 __asan_report_load4_noabort+0x14/0x20 tb_retimer_scan+0xffe/0x1550 [thunderbolt] tb_scan_port+0xa6f/0x2060 [thunderbolt] tb_handle_hotplug+0x17b1/0x3080 [thunderbolt] process_one_work+0x626/0x1100 worker_thread+0x6c8/0xfa0 kthread+0x2c8/0x3a0 ret_from_fork+0x3a/0x80 ret_from_fork_asm+0x1a/0x30

This happens because the loop variable still gets incremented by one so max becomes 3 instead of 2, and this makes the second loop read past the the array declared on the stack.

Fix this by assigning to max directly in the loop body.

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CVE-2024-50227 — thunderbolt: Fix KASAN reported stack out-of-bounds read in tb_retimer_scan()