eth: bnxt: fix kernel panic in the bnxt_get_queue_stats{rx | tx}

Summary

In the Linux kernel, the following vulnerability has been resolved: eth: bnxt: fix kernel panic in the bnxt_get_queue_stats{rx | tx} When qstats-get operation is executed, callbacks of netdev_stats_ops are called. The bnxt_get_queue_stats{rx | tx} collect per-queue stats from sw_stats in the rings. But {rx | tx | cp}_ring are allocated when the interface is up. So, these rings are not allocated when the interface is down. The qstats-get is allowed even if the interface is down. However, the bnxt_get_queue_stats{rx | tx}() accesses cp_ring and tx_ring without null check. So, it needs to avoid accessing rings if the interface is down. Reproducer: ip link set $interface down ./cli.py --spec netdev.yaml --dump qstats-get OR ip link set $interface down python ./stats.py Splat looks like: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1680fa067 P4D 1680fa067 PUD 16be3b067 PMD 0 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 0 UID: 0 PID: 1495 Comm: python3 Not tainted 6.14.0-rc4+ #32 5cd0f999d5a15c574ac72b3e4b907341 Hardware name: ASUS System Product Name/PRIME Z690-P D4, BIOS 0603 11/01/2021 RIP: 0010:bnxt_get_queue_stats_rx+0xf/0x70 [bnxt_en] Code: c6 87 b5 18 00 00 02 eb a2 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 01 RSP: 0018:ffffabef43cdb7e0 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffffffffc04c8710 RCX: 0000000000000000 RDX: ffffabef43cdb858 RSI: 0000000000000000 RDI: ffff8d504e850000 RBP: ffff8d506c9f9c00 R08: 0000000000000004 R09: ffff8d506bcd901c R10: 0000000000000015 R11: ffff8d506bcd9000 R12: 0000000000000000 R13: ffffabef43cdb8c0 R14: ffff8d504e850000 R15: 0000000000000000 FS: 00007f2c5462b080(0000) GS:ffff8d575f600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000167fd0000 CR4: 00000000007506f0 PKRU: 55555554 Call Trace: <TASK> ? __die+0x20/0x70 ? page_fault_oops+0x15a/0x460 ? sched_balance_find_src_group+0x58d/0xd10 ? exc_page_fault+0x6e/0x180 ? asm_exc_page_fault+0x22/0x30 ? bnxt_get_queue_stats_rx+0xf/0x70 [bnxt_en cdd546fd48563c280cfd30e9647efa420db07bf1] netdev_nl_stats_by_netdev+0x2b1/0x4e0 ? xas_load+0x9/0xb0 ? xas_find+0x183/0x1d0 ? xa_find+0x8b/0xe0 netdev_nl_qstats_get_dumpit+0xbf/0x1e0 genl_dumpit+0x31/0x90 netlink_dump+0x1a8/0x360