CVE-2024-38540 bnxt_re: avoid shift undefined behavior in bnxt_qplib_alloc_init_hwq
In the Linux kernel, the following vulnerability has been resolved:

bnxt_re: avoid shift undefined behavior in bnxt_qplib_alloc_init_hwq

Undefined behavior is triggered when bnxt_qplib_alloc_init_hwq is called
with hwq_attr->aux_depth != 0 and hwq_attr->aux_stride == 0.
In that case, "roundup_pow_of_two(hwq_attr->aux_stride)" gets called.
roundup_pow_of_two is documented as undefined for 0.

Fix it in the one caller that had this combination.

The undefined behavior was detected by UBSAN:
  UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13
  shift exponent 64 is too large for 64-bit type 'long unsigned int'
  CPU: 24 PID: 1075 Comm: (udev-worker) Not tainted 6.9.0-rc6+ #4
  Hardware name: Abacus electric, s.r.o. - servis@abacus.cz Super Server/H12SSW-iN, BIOS 2.7 10/25/2023
  Call Trace:
   <TASK>
   dump_stack_lvl+0x5d/0x80
   ubsan_epilogue+0x5/0x30
   __ubsan_handle_shift_out_of_bounds.cold+0x61/0xec
   __roundup_pow_of_two+0x25/0x35 [bnxt_re]
   bnxt_qplib_alloc_init_hwq+0xa1/0x470 [bnxt_re]
   bnxt_qplib_create_qp+0x19e/0x840 [bnxt_re]
   bnxt_re_create_qp+0x9b1/0xcd0 [bnxt_re]
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? __kmalloc+0x1b6/0x4f0
   ? create_qp.part.0+0x128/0x1c0 [ib_core]
   ? __pfx_bnxt_re_create_qp+0x10/0x10 [bnxt_re]
   create_qp.part.0+0x128/0x1c0 [ib_core]
   ib_create_qp_kernel+0x50/0xd0 [ib_core]
   create_mad_qp+0x8e/0xe0 [ib_core]
   ? __pfx_qp_event_handler+0x10/0x10 [ib_core]
   ib_mad_init_device+0x2be/0x680 [ib_core]
   add_client_context+0x10d/0x1a0 [ib_core]
   enable_device_and_get+0xe0/0x1d0 [ib_core]
   ib_register_device+0x53c/0x630 [ib_core]
   ? srso_alias_return_thunk+0x5/0xfbef5
   bnxt_re_probe+0xbd8/0xe50 [bnxt_re]
   ? __pfx_bnxt_re_probe+0x10/0x10 [bnxt_re]
   auxiliary_bus_probe+0x49/0x80
   ? driver_sysfs_add+0x57/0xc0
   really_probe+0xde/0x340
   ? pm_runtime_barrier+0x54/0x90
   ? __pfx___driver_attach+0x10/0x10
   __driver_probe_device+0x78/0x110
   driver_probe_device+0x1f/0xa0
   __driver_attach+0xba/0x1c0
   bus_for_each_dev+0x8f/0xe0
   bus_add_driver+0x146/0x220
   driver_register+0x72/0xd0
   __auxiliary_driver_register+0x6e/0xd0
   ? __pfx_bnxt_re_mod_init+0x10/0x10 [bnxt_re]
   bnxt_re_mod_init+0x3e/0xff0 [bnxt_re]
   ? __pfx_bnxt_re_mod_init+0x10/0x10 [bnxt_re]
   do_one_initcall+0x5b/0x310
   do_init_module+0x90/0x250
   init_module_from_file+0x86/0xc0
   idempotent_init_module+0x121/0x2b0
   __x64_sys_finit_module+0x5e/0xb0
   do_syscall_64+0x82/0x160
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? syscall_exit_to_user_mode_prepare+0x149/0x170
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? syscall_exit_to_user_mode+0x75/0x230
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? do_syscall_64+0x8e/0x160
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? __count_memcg_events+0x69/0x100
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? count_memcg_events.constprop.0+0x1a/0x30
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? handle_mm_fault+0x1f0/0x300
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? do_user_addr_fault+0x34e/0x640
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7f4e5132821d
  Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e3 db 0c 00 f7 d8 64 89 01 48
  RSP: 002b:00007ffca9c906a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
  RAX: ffffffffffffffda RBX: 0000563ec8a8f130 RCX: 00007f4e5132821d
  RDX: 0000000000000000 RSI: 00007f4e518fa07d RDI: 000000000000003b
  RBP: 00007ffca9c90760 R08: 00007f4e513f6b20 R09: 00007ffca9c906f0
  R10: 0000563ec8a8faa0 R11: 0000000000000246 R12: 00007f4e518fa07d
  R13: 0000000000020000 R14: 0000563ec8409e90 R15: 0000563ec8a8fa60
   </TASK>
  ---[ end trace ]---
CVSS v3.1 score: 4.4