From: Bryam Vargas <hexlabsecurity@proton.me> stable inclusion from stable-v6.6.157 commit f9bf05c63b77d000e9c01f3e47af36973887d350 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/19097 CVE: CVE-2026-89965 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- 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: stable@vger.kernel.org Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me> 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.... Signed-off-by: Alison Schofield <alison.schofield@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Lu Jialin <lujialin4@huawei.com> --- drivers/nvdimm/btt.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c index 9e54083505f3..4cfed0a3d142 100644 --- a/drivers/nvdimm/btt.c +++ b/drivers/nvdimm/btt.c @@ -886,6 +886,14 @@ static int discover_arenas(struct btt *btt) 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), -- 2.34.1