um: Fix out-of-bounds read in LDT setup

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: um: Fix out-of-bounds read in LDT setup syscall_stub_data() expects the data_count parameter to be the number of longs, not bytes. ================================================================== BUG: KASAN: stack-out-of-bounds in syscall_stub_data+0x70/0xe0 Read of size 128 at addr 000000006411f6f0 by task swapper/1 CPU: 0 PID: 1 Comm: swapper Not tainted 5.18.0+ #18 Call Trace: show_stack.cold+0x166/0x2a7 __dump_stack+0x3a/0x43 dump_stack_lvl+0x1f/0x27 print_report.cold+0xdb/0xf81 kasan_report+0x119/0x1f0 kasan_check_range+0x3a3/0x440 memcpy+0x52/0x140 syscall_stub_data+0x70/0xe0 write_ldt_entry+0xac/0x190 init_new_ldt+0x515/0x960 init_new_context+0x2c4/0x4d0 mm_init.constprop.0+0x5ed/0x760 mm_alloc+0x118/0x170 0x60033f48 do_one_initcall+0x1d7/0x860 0x60003e7b kernel_init+0x6e/0x3d4 new_thread_handler+0x1e7/0x2c0 The buggy address belongs to stack of task swapper/1 and is located at offset 64 in frame: init_new_ldt+0x0/0x960 This frame has 2 objects: [32, 40) 'addr' [64, 80) 'desc' ==================================================================

References

• https://git.kernel.org/stable/c/668ca34a428d6ffc0f99a1a6a9b661a288d4183b
• https://git.kernel.org/stable/c/ef1dc929a1e5fa1b2d842256db9fb8710d3be910
• https://git.kernel.org/stable/c/3549ab4b962cf619e8c55484a0d870a34b3f845f
• https://git.kernel.org/stable/c/9caad70819aef3431abaf73ba5163b55b161aba0
• https://git.kernel.org/stable/c/cf0dabc37446c5ee538ae7b4c467ab0e53fa5463
• https://git.kernel.org/stable/c/10995a382271254bd276627ec74136da4a23c4a6
• https://git.kernel.org/stable/c/24ca648bf5f72ed8878cf09b5d4431935779681e
• https://git.kernel.org/stable/c/91e5ba2af2d729d5126aefd5aa3eadc69b8426e5
• https://git.kernel.org/stable/c/2a4a62a14be1947fa945c5c11ebf67326381a568