In the Linux kernel, the following vulnerability has been resolved: ice: fix race condition in...

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

ice: fix race condition in TX timestamp ring cleanup

Fix a race condition between ice_free_tx_tstamp_ring() and ice_tx_map() that can cause a NULL pointer dereference.

ice_free_tx_tstamp_ring currently clears the ICE_TX_FLAGS_TXTIME flag after NULLing the tstamp_ring. This could allow a concurrent ice_tx_map call on another CPU to dereference the tstamp_ring, which could lead to a NULL pointer dereference.

CPU A:ice_free_tx_tstamp_ring() | CPU B:ice_tx_map() --------------------------------|--------------------------------- tx_ring->tstamp_ring = NULL | | ice_is_txtime_cfg() -> true | tstamp_ring = tx_ring->tstamp_ring | tstamp_ring->count // NULL deref! flags &= ~ICE_TX_FLAGS_TXTIME |

Fix by:

1. Reordering ice_free_tx_tstamp_ring() to clear the flag before NULLing the pointer, with smp_wmb() to ensure proper ordering.
2. Adding smp_rmb() in ice_tx_map() after the flag check to order the flag read before the pointer read, using READ_ONCE() for the pointer, and adding a NULL check as a safety net.
3. Converting tx_ring->flags from u8 to DECLARE_BITMAP() and using atomic bitops (set_bit(), clear_bit(), test_bit()) for all flag operations throughout the driver:
   • ICE_TX_RING_FLAGS_XDP
   • ICE_TX_RING_FLAGS_VLAN_L2TAG1
   • ICE_TX_RING_FLAGS_VLAN_L2TAG2
   • ICE_TX_RING_FLAGS_TXTIME