net/bnx2x: Prevent access to a freed page in page_pool
In the Linux kernel, the following vulnerability has been resolved:

net/bnx2x: Prevent access to a freed page in page_pool

Fix race condition leading to system crash during EEH error handling

During EEH error recovery, the bnx2x driver's transmit timeout logic
could cause a race condition when handling reset tasks. The
bnx2x_tx_timeout() schedules reset tasks via bnx2x_sp_rtnl_task(),
which ultimately leads to bnx2x_nic_unload(). In bnx2x_nic_unload()
SGEs are freed using bnx2x_free_rx_sge_range(). However, this could
overlap with the EEH driver's attempt to reset the device using
bnx2x_io_slot_reset(), which also tries to free SGEs. This race
condition can result in system crashes due to accessing freed memory
locations in bnx2x_free_rx_sge()

799  static inline void bnx2x_free_rx_sge(struct bnx2x *bp,
800				struct bnx2x_fastpath *fp, u16 index)
801  {
802	struct sw_rx_page *sw_buf = &fp->rx_page_ring[index];
803     struct page *page = sw_buf->page;
....
where sw_buf was set to NULL after the call to dma_unmap_page()
by the preceding thread.

    EEH: Beginning: 'slot_reset'
    PCI 0011:01:00.0#10000: EEH: Invoking bnx2x->slot_reset()
    bnx2x: [bnx2x_io_slot_reset:14228(eth1)]IO slot reset initializing...
    bnx2x 0011:01:00.0: enabling device (0140 -> 0142)
    bnx2x: [bnx2x_io_slot_reset:14244(eth1)]IO slot reset --> driver unload
    Kernel attempted to read user page (0) - exploit attempt? (uid: 0)
    BUG: Kernel NULL pointer dereference on read at 0x00000000
    Faulting instruction address: 0xc0080000025065fc
    Oops: Kernel access of bad area, sig: 11 [#1]
    .....
    Call Trace:
    [c000000003c67a20] [c00800000250658c] bnx2x_io_slot_reset+0x204/0x610 [bnx2x] (unreliable)
    [c000000003c67af0] [c0000000000518a8] eeh_report_reset+0xb8/0xf0
    [c000000003c67b60] [c000000000052130] eeh_pe_report+0x180/0x550
    [c000000003c67c70] [c00000000005318c] eeh_handle_normal_event+0x84c/0xa60
    [c000000003c67d50] [c000000000053a84] eeh_event_handler+0xf4/0x170
    [c000000003c67da0] [c000000000194c58] kthread+0x1c8/0x1d0
    [c000000003c67e10] [c00000000000cf64] ret_from_kernel_thread+0x5c/0x64

To solve this issue, we need to verify page pool allocations before
freeing.