5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bryam Vargas <redacted>
commit 6a1f2e5ed9267ca19187038ac635393c165213ac upstream.
The BTT info block's nfree field, the number of reserve free blocks, is
read from the medium without validation. btt_freelist_init() and
btt_rtt_init() size the per-lane freelist[] and rtt[] arrays by nfree,
but the I/O path indexes them by the lane from nd_region_acquire_lane(),
which is bounded by nd_region->num_lanes (ND_MAX_LANES), not by nfree.
A crafted or foreign arena whose nfree is below the lane count makes
freelist[lane]/rtt[lane] run past the allocation: an out-of-bounds write.
btt.rst documents the nlanes = min(nfree, num_cpus) invariant, which the
code does not currently honor: num_lanes is ND_MAX_LANES regardless of
nfree. Reject an arena whose nfree is below num_lanes at discovery,
before the per-lane arrays are allocated, enforcing that invariant.
Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
Cc: <redacted>
Signed-off-by: Bryam Vargas <redacted>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260620-b4-disp-88b2514b-v1-1-3834e707d232@proton.me (local)
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/nvdimm/btt.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -887,6 +887,14 @@ static int discover_arenas(struct btt *b
arena->external_lba_start = cur_nlba;
parse_arena_meta(arena, super, cur_off);
+ if (arena->nfree < btt->nd_region->num_lanes) {
+ dev_err(to_dev(arena),
+ "nfree %u smaller than lane count %d\n",
+ arena->nfree, btt->nd_region->num_lanes);
+ ret = -ENODEV;
+ goto out;
+ }
+
ret = log_set_indices(arena);
if (ret) {
dev_err(to_dev(arena),