CVE-2024-44933: Out-of-bounds Write

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

bnxt_en : Fix memory out-of-bounds in bnxt_fill_hw_rss_tbl()

A recent commit has modified the code in __bnxt_reserve_rings() to set the default RSS indirection table to default only when the number of RX rings is changing. While this works for newer firmware that requires RX ring reservations, it causes the regression on older firmware not requiring RX ring resrvations (BNXT_NEW_RM() returns false).

With older firmware, RX ring reservations are not required and so hw_resc->resv_rx_rings is not always set to the proper value. The comparison:

if (old_rx_rings != bp->hw_resc.resv_rx_rings)

in __bnxt_reserve_rings() may be false even when the RX rings are changing. This will cause __bnxt_reserve_rings() to skip setting the default RSS indirection table to default to match the current number of RX rings. This may later cause bnxt_fill_hw_rss_tbl() to use an out-of-range index.

We already have bnxt_check_rss_tbl_no_rmgr() to handle exactly this scenario. We just need to move it up in bnxt_need_reserve_rings() to be called unconditionally when using older firmware. Without the fix, if the TX rings are changing, we'll skip the bnxt_check_rss_tbl_no_rmgr() call and __bnxt_reserve_rings() may also skip the bnxt_set_dflt_rss_indir_tbl() call for the reason explained in the last paragraph. Without setting the default RSS indirection table to default, it causes the regression:

BUG: KASAN: slab-out-of-bounds in __bnxt_hwrm_vnic_set_rss+0xb79/0xe40 Read of size 2 at addr ffff8881c5809618 by task ethtool/31525 Call Trace: __bnxt_hwrm_vnic_set_rss+0xb79/0xe40 bnxt_hwrm_vnic_rss_cfg_p5+0xf7/0x460 __bnxt_setup_vnic_p5+0x12e/0x270 __bnxt_open_nic+0x2262/0x2f30 bnxt_open_nic+0x5d/0xf0 ethnl_set_channels+0x5d4/0xb30 ethnl_default_set_doit+0x2f1/0x620