[PATCH v4 0/6] cxl: Sashiko bug fixes

[Richard Cheng <icheng@nvidia.com>]

Six independent, pre-existing bugs in the CXL core, reported by
sashiko.

Patch 1: Get/Set Feature derive each mailbox command's offset from the
starting offset plus the amount of data already transferred, then store
it in a 16-bit field. A large offset/count supplied through fwctl can
cause a later offset to exceed the representable feature extent and be
truncated by cpu_to_le16(), targeting the wrong feature data. Reject
invalid ranges up front.

Change cxl_get_feature() to return ssize_t so invalid input and mailbox
failures are reported as negative errno instead of being conflated with
a zero-byte result. Update all EDAC callers for the signed return
contract while preserving the existing fwctl RPC response behavior.

Patch 2: cxl_get_poison_unmapped() aborted its whole partition sweep on
the first fully-mapped partition, silently skipping unmapped poison in
all later partitions. Skip that partition instead.

Patch 3: the same function tolerated the -EFAULT a RAM partition returns
for Get Poison List but left it in rc, so a benign fault on the last
scanned partition surfaced as a spurious read failure. Clear rc, as
poison_by_decoder() already does.

Patch 4: the same function also ignored the ctx->offset handoff from
poison_by_decoder() and derived its scan start from the highest DPA
allocation, so the DPA of allocated-but-uncommitted decoders was never
scanned by either phase. Resume the sweep at ctx->offset.

Patch 5: cxl_get_poison_by_memdev() overwrote rc on each partition
query, so an earlier partition's failure was masked by a later success
and unscanned poison was reported as a clean list. Stop on any error
not tolerated as a RAM -EFAULT.

Patch 6: poison_by_decoder() assumed every decoder with a DPA reservation
was assigned to a partition. Malformed device DPA metadata can leave
dpa_res set while part remains -1, causing a poison scan to access
before the partition array. Reject such decoders before the lookup.

Changes since v3 [1]:
- Patch 1~5: Rebase onto cxl/next
- Patch 6: New patch

[1]:
https://lore.kernel.org/linux-cxl/20260708074228.43654-1-icheng@nvidia.com/

Richard Cheng (6):
  cxl/features: Reject feature offset that overflows 16-bit field
  cxl/region: Scan all partitions for unmapped poison
  cxl/region: Don't leak tolerated RAM -EFAULT from unmapped poison scan
  cxl/region: Start unmapped poison scan at the committed decoder
    boundary
  cxl/memdev: Don't overwrite the error from an earlier partition poison
    query
  cxl/region: Reject poison scan for decoder without a partition

 drivers/cxl/core/core.h     |  8 ++++----
 drivers/cxl/core/edac.c     | 20 +++++++++++++++-----
 drivers/cxl/core/features.c | 28 ++++++++++++++++++----------
 drivers/cxl/core/memdev.c   |  2 ++
 drivers/cxl/core/region.c   | 15 ++++++++-------
 5 files changed, 47 insertions(+), 26 deletions(-)


base-commit: 7098e9cd98a05c0c5de2fae0c2465f9d966fdd07
-- 
2.43.0