wifi: mac80211: minstrel_ht: validate fixed rate index

The fixed_rate_idx debugfs file is a plain u32 attribute, so any value
can be written to it.  minstrel_ht_update_stats() then copies the value
into mi->max_tp_rate[] and mi->max_prob_rate, and
minstrel_ht_set_rate() uses MI_RATE_GROUP()/MI_RATE_IDX() to index
minstrel_mcs_groups[] (42 entries) and mi->groups[].rates[] (10 entries)
with it.

Writing e.g. 65535 selects group 4095 and rate index 15, far outside
both arrays.  The out-of-bounds entries are dereferenced and updated as
struct minstrel_rate_stats (retry counts, etc.), so the invalid index
corrupts adjacent kernel memory.  With CONFIG_UBSAN_BOUNDS the access is
reported as an array-index-out-of-bounds in minstrel_ht_set_rate().

Only a valid group/rate pair, or U32_MAX to disable fixed rate
processing, can be used safely, so reject any other value when the
debugfs file is written.

The file is only reachable through a root-only debugfs mount, so this is
not a privilege boundary.  The out-of-bounds access is still a bug that
must not be reachable through a writable debugfs attribute.

Fixes: 24f7580e852b ("minstrel_ht: fixed rate mode through debugfs")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Assisted-by: LLM
Signed-off-by: Yuqi Xu <xuyuqiabc@gmail.com>
Reviewed-by: Ren Wei <weir@nebusec.ai>
Link: https://patch.msgid.link/288e6f6d30dc82ff40da502755e6666982f6b735.1789798000.git.xuyuqiabc@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

0 files changed, 0 insertions, 0 deletions