[PATCH v6 0/7] cxl: Sashiko bug fixes

[PATCH v6 0/7] cxl: Sashiko bug fixes

[Richard Cheng]

Seven 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.

Patch 7: the Get and Set Feature fwctl handlers converted all helper
failures into normal RPC responses, sometimes with a SUCCESS device
status. Propagate delivery failures as ioctl errors while continuing to
report actual device errors through rpc_out->retval.

Changes since v5 [1]:
- Patch 7: Remove the redundant terminal CXL_MBOX_CMD_RC_SUCCESS
  assignments. (Dave Jiang)

[1]:
https://lore.kernel.org/linux-cxl/20260813034538.13189-1-icheng@nvidia.com/

Richard Cheng (7):
  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
  cxl/fwctl: Propagate feature RPC delivery errors

 drivers/cxl/core/core.h     |  8 +++----
 drivers/cxl/core/edac.c     | 20 +++++++++++++-----
 drivers/cxl/core/features.c | 42 ++++++++++++++++++++++---------------
 drivers/cxl/core/memdev.c   |  2 ++
 drivers/cxl/core/region.c   | 15 ++++++-------
 5 files changed, 54 insertions(+), 33 deletions(-)


base-commit: 7098e9cd98a05c0c5de2fae0c2465f9d966fdd07
-- 
2.43.0

[PATCH v6 1/7] cxl/features: Reject feature offset that overflows 16-bit field

[Richard Cheng]

cxl_get_feature() and cxl_set_feature() build 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 user-controlled fwctl
offset and transfer size can exceed the feature extent, allowing a later
offset to be truncated by cpu_to_le16() and target the wrong feature
data.

Reject requests whose transfer size exceeds the remaining 16-bit feature
range. Express the check as "size > U16_MAX - offset" so the validation
itself cannot wrap on 32-bit systems.

Change cxl_get_feature() to return ssize_t so invalid input and mailbox
failures are reported as negative errno rather than being conflated with
a zero-byte result. Update the EDAC callers to handle negative results.
Keep fwctl behavior unchanged by translating helper failures to the same
header-only RPC response carrying the CXL mailbox return code.

Fixes: 5e5ac21f629d ("cxl/mbox: Add GET_FEATURE mailbox command")
Fixes: 14d502cc2718 ("cxl/mbox: Add SET_FEATURE mailbox command")
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 drivers/cxl/core/core.h     |  8 ++++----
 drivers/cxl/core/edac.c     | 20 +++++++++++++++-----
 drivers/cxl/core/features.c | 28 ++++++++++++++++++----------
 3 files changed, 37 insertions(+), 19 deletions(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 35eaf636adc9..bb380ec6daeb 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -217,10 +217,10 @@ int cxl_port_get_possible_dports(struct cxl_port *port);
 #ifdef CONFIG_CXL_FEATURES
 struct cxl_feat_entry *
 cxl_feature_info(struct cxl_features_state *cxlfs, const uuid_t *uuid);
-size_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
-		       enum cxl_get_feat_selection selection,
-		       void *feat_out, size_t feat_out_size, u16 offset,
-		       u16 *return_code);
+ssize_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
+			enum cxl_get_feat_selection selection,
+			void *feat_out, size_t feat_out_size, u16 offset,
+			u16 *return_code);
 int cxl_set_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
 		    u8 feat_version, const void *feat_data,
 		    size_t feat_data_size, u32 feat_flag, u16 offset,
diff --git a/drivers/cxl/core/edac.c b/drivers/cxl/core/edac.c
index b321971fef58..f1df4b5cfe5b 100644
--- a/drivers/cxl/core/edac.c
+++ b/drivers/cxl/core/edac.c
@@ -78,7 +78,7 @@ static int cxl_mem_scrub_get_attrbs(struct cxl_mailbox *cxl_mbox, u8 *cap,
 				    u16 *cycle, u8 *flags, u8 *min_cycle)
 {
 	size_t rd_data_size = sizeof(struct cxl_scrub_rd_attrbs);
-	size_t data_size;
+	ssize_t data_size;
 	struct cxl_scrub_rd_attrbs *rd_attrbs __free(kfree) =
 		kzalloc(rd_data_size, GFP_KERNEL);
 	if (!rd_attrbs)
@@ -87,6 +87,8 @@ static int cxl_mem_scrub_get_attrbs(struct cxl_mailbox *cxl_mbox, u8 *cap,
 	data_size = cxl_get_feature(cxl_mbox, &CXL_FEAT_PATROL_SCRUB_UUID,
 				    CXL_GET_FEAT_SEL_CURRENT_VALUE, rd_attrbs,
 				    rd_data_size, 0, NULL);
+	if (data_size < 0)
+		return data_size;
 	if (!data_size)
 		return -EIO;
 
@@ -551,7 +553,7 @@ static int cxl_mem_ecs_get_attrbs(struct device *dev,
 	struct cxl_mailbox *cxl_mbox = &cxlmd->cxlds->cxl_mbox;
 	struct cxl_ecs_fru_rd_attrbs *fru_rd_attrbs;
 	size_t rd_data_size;
-	size_t data_size;
+	ssize_t data_size;
 
 	rd_data_size = cxl_ecs_ctx->get_feat_size;
 
@@ -563,6 +565,8 @@ static int cxl_mem_ecs_get_attrbs(struct device *dev,
 	data_size = cxl_get_feature(cxl_mbox, &CXL_FEAT_ECS_UUID,
 				    CXL_GET_FEAT_SEL_CURRENT_VALUE, rd_attrbs,
 				    rd_data_size, 0, NULL);
+	if (data_size < 0)
+		return data_size;
 	if (!data_size)
 		return -EIO;
 
@@ -583,7 +587,7 @@ static int cxl_mem_ecs_set_attrbs(struct device *dev,
 	struct cxl_ecs_fru_wr_attrbs *fru_wr_attrbs;
 	size_t rd_data_size, wr_data_size;
 	u16 num_media_frus, count;
-	size_t data_size;
+	ssize_t data_size;
 
 	num_media_frus = cxl_ecs_ctx->num_media_frus;
 	rd_data_size = cxl_ecs_ctx->get_feat_size;
@@ -596,6 +600,8 @@ static int cxl_mem_ecs_set_attrbs(struct device *dev,
 	data_size = cxl_get_feature(cxl_mbox, &CXL_FEAT_ECS_UUID,
 				    CXL_GET_FEAT_SEL_CURRENT_VALUE, rd_attrbs,
 				    rd_data_size, 0, NULL);
+	if (data_size < 0)
+		return data_size;
 	if (!data_size)
 		return -EIO;
 
@@ -1264,7 +1270,7 @@ cxl_mem_sparing_get_attrbs(struct cxl_mem_sparing_context *cxl_sparing_ctx)
 	struct cxl_memdev *cxlmd = cxl_sparing_ctx->cxlmd;
 	struct cxl_mailbox *cxl_mbox = &cxlmd->cxlds->cxl_mbox;
 	u16 restriction_flags;
-	size_t data_size;
+	ssize_t data_size;
 	u16 return_code;
 	struct cxl_memdev_sparing_rd_attrbs *rd_attrbs __free(kfree) =
 		kzalloc(rd_data_size, GFP_KERNEL);
@@ -1274,6 +1280,8 @@ cxl_mem_sparing_get_attrbs(struct cxl_mem_sparing_context *cxl_sparing_ctx)
 	data_size = cxl_get_feature(cxl_mbox, &cxl_sparing_ctx->repair_uuid,
 				    CXL_GET_FEAT_SEL_CURRENT_VALUE, rd_attrbs,
 				    rd_data_size, 0, &return_code);
+	if (data_size < 0)
+		return data_size;
 	if (!data_size)
 		return -EIO;
 
@@ -1750,7 +1758,7 @@ static int cxl_mem_ppr_get_attrbs(struct cxl_ppr_context *cxl_ppr_ctx)
 	struct cxl_memdev *cxlmd = cxl_ppr_ctx->cxlmd;
 	struct cxl_mailbox *cxl_mbox = &cxlmd->cxlds->cxl_mbox;
 	u16 restriction_flags;
-	size_t data_size;
+	ssize_t data_size;
 	u16 return_code;
 
 	struct cxl_memdev_ppr_rd_attrbs *rd_attrbs __free(kfree) =
@@ -1761,6 +1769,8 @@ static int cxl_mem_ppr_get_attrbs(struct cxl_ppr_context *cxl_ppr_ctx)
 	data_size = cxl_get_feature(cxl_mbox, &cxl_ppr_ctx->repair_uuid,
 				    CXL_GET_FEAT_SEL_CURRENT_VALUE, rd_attrbs,
 				    rd_data_size, 0, &return_code);
+	if (data_size < 0)
+		return data_size;
 	if (!data_size)
 		return -EIO;
 
diff --git a/drivers/cxl/core/features.c b/drivers/cxl/core/features.c
index ba6d2a5acb74..8d44ce829497 100644
--- a/drivers/cxl/core/features.c
+++ b/drivers/cxl/core/features.c
@@ -220,10 +220,10 @@ int devm_cxl_setup_features(struct cxl_dev_state *cxlds)
 }
 EXPORT_SYMBOL_NS_GPL(devm_cxl_setup_features, "CXL");
 
-size_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
-		       enum cxl_get_feat_selection selection,
-		       void *feat_out, size_t feat_out_size, u16 offset,
-		       u16 *return_code)
+ssize_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
+			enum cxl_get_feat_selection selection,
+			void *feat_out, size_t feat_out_size, u16 offset,
+			u16 *return_code)
 {
 	size_t data_to_rd_size;
 	struct cxl_mbox_get_feat_in pi;
@@ -235,7 +235,10 @@ size_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
 		*return_code = CXL_MBOX_CMD_RC_INPUT;
 
 	if (!feat_out || !feat_out_size)
-		return 0;
+		return -EINVAL;
+
+	if (feat_out_size > U16_MAX - offset)
+		return -EINVAL;
 
 	uuid_copy(&pi.uuid, feat_uuid);
 	pi.selection = selection;
@@ -259,7 +262,7 @@ size_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
 		if (rc < 0 || !mbox_cmd.size_out) {
 			if (return_code)
 				*return_code = mbox_cmd.return_code;
-			return 0;
+			return rc < 0 ? rc : -EIO;
 		}
 		data_rcvd_size += mbox_cmd.size_out;
 	} while (data_rcvd_size < feat_out_size);
@@ -288,6 +291,9 @@ int cxl_set_feature(struct cxl_mailbox *cxl_mbox,
 	if (return_code)
 		*return_code = CXL_MBOX_CMD_RC_INPUT;
 
+	if (feat_data_size > U16_MAX - offset)
+		return -EINVAL;
+
 	struct cxl_mbox_set_feat_in *pi __free(kfree) =
 			kzalloc(cxl_mbox->payload_size, GFP_KERNEL);
 	if (!pi)
@@ -462,6 +468,7 @@ static void *cxlctl_get_feature(struct cxl_features_state *cxlfs,
 	const struct cxl_mbox_get_feat_in *feat_in;
 	u16 offset, count, return_code;
 	size_t out_size = *out_len;
+	ssize_t data_size;
 
 	if (rpc_in->op_size != sizeof(*feat_in))
 		return ERR_PTR(-EINVAL);
@@ -482,16 +489,17 @@ static void *cxlctl_get_feature(struct cxl_features_state *cxlfs,
 	if (!rpc_out)
 		return ERR_PTR(-ENOMEM);
 
-	out_size = cxl_get_feature(cxl_mbox, &feat_in->uuid,
-				   feat_in->selection, rpc_out->payload,
-				   count, offset, &return_code);
+	data_size = cxl_get_feature(cxl_mbox, &feat_in->uuid,
+				    feat_in->selection, rpc_out->payload,
+				    count, offset, &return_code);
 	*out_len = sizeof(struct fwctl_rpc_cxl_out);
-	if (!out_size) {
+	if (data_size <= 0) {
 		rpc_out->size = 0;
 		rpc_out->retval = return_code;
 		return no_free_ptr(rpc_out);
 	}
 
+	out_size = data_size;
 	rpc_out->size = out_size;
 	rpc_out->retval = CXL_MBOX_CMD_RC_SUCCESS;
 	*out_len += out_size;
-- 
2.43.0

[PATCH v6 2/7] cxl/region: Scan all partitions for unmapped poison

[Richard Cheng]

cxl_get_poison_unmapped() sweeps the unmapped tail of each partition
from ctx->part onward. A fully-mapped partition has no unmapped tail,
it's a normal per-partition state, but the loop treated it with break,
aborting the whole sweep and silently skipping unmapped poison in all
later partition. Use continue so a fully-mapped partition is skipped and
later partitions are still scanned.

Fixes: be5cbd0840275 ("cxl: Kill enum cxl_decoder_mode")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
Changelog:

v1->v2:
    - Tweak commit message
---
 drivers/cxl/core/region.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 27e63e6dab7c..b03f30c04d35 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2928,7 +2928,7 @@ static int cxl_get_poison_unmapped(struct cxl_memdev *cxlmd,
 			offset = res->start;
 		length = res->end - offset + 1;
 		if (!length)
-			break;
+			continue;
 		rc = cxl_mem_get_poison(cxlmd, offset, length, NULL);
 		if (rc == -EFAULT && cxlds->part[i].mode == CXL_PARTMODE_RAM)
 			continue;
-- 
2.43.0

Re: [PATCH v6 2/7] cxl/region: Scan all partitions for unmapped poison

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Missing bounds check on hardware-supplied `po->count` in `cxl_mem_get_poison` leads to out-of-bounds read of kernel memory.
--

commit f52d52e430dd176144d958a0ce4c3eb954ee8a23
Author: Richard Cheng <icheng@nvidia.com>

cxl/region: Scan all partitions for unmapped poison

cxl_get_poison_unmapped() sweeps the unmapped tail of each partition
from ctx->part onward. A fully-mapped partition has no unmapped tail,
it's a normal per-partition state, but the loop treated it with break,
aborting the whole sweep and silently skipping unmapped poison in all
later partition. Use continue so a fully-mapped partition is skipped and
later partitions are still scanned.

> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 27e63e6dab7c8..b03f30c04d350 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2928,7 +2928,7 @@ static int cxl_get_poison_unmapped(struct cxl_memdev *cxlmd,
>  			offset = res->start;
>  		length = res->end - offset + 1;
>  		if (!length)
> -			break;
> +			continue;
>  		rc = cxl_mem_get_poison(cxlmd, offset, length, NULL);

[Severity: High]
This is a pre-existing issue, but I noticed a potential out-of-bounds read in
cxl_mem_get_poison() when it processes the hardware-supplied poison records.

Looking at cxl_mem_get_poison() in drivers/cxl/core/mbox.c, the function
uses an untrusted hardware value po->count in the loop:

	for (int i = 0; i < le16_to_cpu(po->count); i++)
		trace_cxl_poison(cxlmd, cxlr, &po->record[i],
				 po->flags, po->overflow_ts,
				 CXL_POISON_TRACE_LIST);

Could a buggy or malicious CXL device return an arbitrarily large po->count
value (for example 0xFFFF) that doesn't fit within the returned payload size
or the dynamically allocated mds->poison.list_out buffer?

If this happens, does this loop read past the end of the allocated memory,
potentially causing a kernel panic or information leak via ftrace?

>  		if (rc == -EFAULT && cxlds->part[i].mode == CXL_PARTMODE_RAM)
>  			continue;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260826014508.9989-1-icheng@nvidia.com?part=2

[PATCH v6 3/7] cxl/region: Don't leak tolerated RAM -EFAULT from unmapped poison scan

[Richard Cheng]

cxl_get_poison_unmapped() tolerates the -EFAULT a RAM partition returns
for Get Poison List by skipping that partition, but left rc holding the
error. If the tolerated RAM fault was the last poison query before the
loop ended, the function returned a spurious -EFAULT and the poison-list
read failed even though enumeration succeeded. Reset rc to 0 when
tolerating the fault, matching poison_by_decoder().

Fixes: be5cbd0840275 ("cxl: Kill enum cxl_decoder_mode")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 drivers/cxl/core/region.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index b03f30c04d35..ddf12075b95c 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2930,8 +2930,10 @@ static int cxl_get_poison_unmapped(struct cxl_memdev *cxlmd,
 		if (!length)
 			continue;
 		rc = cxl_mem_get_poison(cxlmd, offset, length, NULL);
-		if (rc == -EFAULT && cxlds->part[i].mode == CXL_PARTMODE_RAM)
+		if (rc == -EFAULT && cxlds->part[i].mode == CXL_PARTMODE_RAM) {
+			rc = 0;
 			continue;
+		}
 		if (rc)
 			break;
 	}
-- 
2.43.0

[PATCH v6 4/7] cxl/region: Start unmapped poison scan at the committed decoder boundary

[Richard Cheng]

poison_by_decoder() stops at the last committed decoder and records the
handoff in ctx->offset, but cxl_get_poison_unmapped() ignores it and
starts after the highest DPA allocation instead. Allocation exist for
uncommitted decoders too, so their DPA is skipped by both phases and
poison there is never reported. Resume the scan at ctx->offset, and scan
later partitions in full, restoring the pre-rewrite behavior.

Fixes: be5cbd084027 ("cxl: Kill enum cxl_decoder_mode")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
Changelog:

v1->v2:
    - New added patch ( sashiko's report )
---
 drivers/cxl/core/region.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index ddf12075b95c..b7dc5d4988da 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2907,7 +2907,6 @@ static int cxl_get_poison_unmapped(struct cxl_memdev *cxlmd,
 {
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	const struct resource *res;
-	struct resource *p, *last;
 	u64 offset, length;
 	int rc = 0;
 
@@ -2920,10 +2919,8 @@ static int cxl_get_poison_unmapped(struct cxl_memdev *cxlmd,
 	 */
 	for (int i = ctx->part; i < cxlds->nr_partitions; i++) {
 		res = &cxlds->part[i].res;
-		for (p = res->child, last = NULL; p; p = p->sibling)
-			last = p;
-		if (last)
-			offset = last->end + 1;
+		if (i == ctx->part)
+			offset = ctx->offset;
 		else
 			offset = res->start;
 		length = res->end - offset + 1;
-- 
2.43.0

[PATCH v6 5/7] cxl/memdev: Don't overwrite the error from an earlier partition poison query

[Richard Cheng]

cxl_get_poison_by_memdev() queries Get Poison List per partition but
never checks the result inside the loop, so a later partition's success
overwrites an earlier partition's failure and the whole scan reports
success while that partition's poison went unlisted. Before the loop
conversion the PMEM query returned early on error. Stop the loop on any
error not already tolerated as a RAM -EFAULT.

Fixes: be5cbd084027 ("cxl: Kill enum cxl_decoder_mode")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
Changelog:

v1->v2:
    - New added patch ( sashiko-bot's report )
---
 drivers/cxl/core/memdev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index b3419df586b9..e39b3d13fd56 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -231,6 +231,8 @@ static int cxl_get_poison_by_memdev(struct cxl_memdev *cxlmd)
 		 */
 		if (rc == -EFAULT && cxlds->part[i].mode == CXL_PARTMODE_RAM)
 			rc = 0;
+		if (rc)
+			break;
 	}
 	return rc;
 }
-- 
2.43.0

Re: [PATCH v6 5/7] cxl/memdev: Don't overwrite the error from an earlier partition poison query

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Unvalidated `po->count` from hardware payload causes an out-of-bounds memory read that gets exposed to userspace via the `cxl_poison` tracepoint.
--

commit b8896ead9022e537cefc70198cd640048454c1cf
Author: Richard Cheng <icheng@nvidia.com>

cxl/memdev: Don't overwrite the error from an earlier partition poison query

cxl_get_poison_by_memdev() queries Get Poison List per partition but
never checks the result inside the loop, so a later partition's success
overwrites an earlier partition's failure and the whole scan reports
success while that partition's poison went unlisted. Before the loop
conversion the PMEM query returned early on error. Stop the loop on any
error not already tolerated as a RAM -EFAULT.

> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index b3419df586b9c..e39b3d13fd566 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -231,6 +231,8 @@ static int cxl_get_poison_by_memdev(struct cxl_memdev *cxlmd)
>  		 */
>  		if (rc == -EFAULT && cxlds->part[i].mode == CXL_PARTMODE_RAM)
>  			rc = 0;
> +		if (rc)
> +			break;
>  	}
>  	return rc;
>  }

[Severity: High]
This is a pre-existing issue, but I noticed a potential out-of-bounds read
triggered when cxl_get_poison_by_memdev() calls cxl_mem_get_poison() earlier
in this loop.

Looking at cxl_mem_get_poison() in drivers/cxl/core/mbox.c:

drivers/cxl/core/mbox.c:cxl_mem_get_poison() {
    ...
		rc = cxl_internal_send_cmd(cxl_mbox, &mbox_cmd);
		if (rc)
			break;

		if (!le16_to_cpu(po->count)) {
			dev_dbg(&cxlmd->dev, "Poison empty payload!\n");
			break;
		}

		for (int i = 0; i < le16_to_cpu(po->count); i++)
			trace_cxl_poison(cxlmd, cxlr, &po->record[i],
					 po->flags, po->overflow_ts,
					 CXL_POISON_TRACE_LIST);
    ...
}

Does this code trust the unvalidated po->count value from the hardware
payload?

If a device returns an artificially large po->count (up to 65535), the loop
appears to read beyond the bounds of the mds->poison.list_out buffer and expose
adjacent kernel memory to userspace via the cxl_poison tracepoint.

Could we bound po->count to mbox_cmd.size_out or the buffer capacity
to prevent this?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260826014508.9989-1-icheng@nvidia.com?part=5

[PATCH v6 6/7] cxl/region: Reject poison scan for decoder without a partition

[Richard Cheng]

__cxl_dpa_reserve() may leave cxled->part at -1 when a decoder's DPA
range doesn't map to any reported partition, while still keeping
dpa_res. poison_by_decoder() then indexes cxlds->part[-1], causing an
out-of-bounds read when poison collection is triggered.

Return -ENODEV before accessing the partition array when no partition was
assigned.

Fixes: be5cbd084027 ("cxl: Kill enum cxl_decoder_mode")
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 drivers/cxl/core/region.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index b7dc5d4988da..afe3fb57b7fe 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2954,6 +2954,8 @@ static int poison_by_decoder(struct device *dev, void *arg)
 	cxled = to_cxl_endpoint_decoder(dev);
 	if (!cxled->dpa_res)
 		return rc;
+	if (cxled->part < 0)
+		return -ENODEV;
 
 	cxlmd = cxled_to_memdev(cxled);
 	cxlds = cxlmd->cxlds;
-- 
2.43.0

Re: [PATCH v6 6/7] cxl/region: Reject poison scan for decoder without a partition

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Premature iteration abort in poison collection when a decoder lacks a partition.
--

commit 414c0bfc48b7f7d14076be9625353a3a1ecb8ff9
Author: Richard Cheng <icheng@nvidia.com>

cxl/region: Reject poison scan for decoder without a partition

This commit returns -ENODEV when attempting to scan for poison on a
decoder without a valid partition. This prevents an out-of-bounds read
of the partition array during poison collection.

> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index b7dc5d4988da7..afe3fb57b7fe2 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2954,6 +2954,8 @@ static int poison_by_decoder(struct device *dev, void *arg)
>  	cxled = to_cxl_endpoint_decoder(dev);
>  	if (!cxled->dpa_res)
>  		return rc;
> +	if (cxled->part < 0)
> +		return -ENODEV;

[Severity: Medium]
When poison_by_decoder() returns a non-zero error code like -ENODEV,
doesn't it cause the caller's iteration to abort entirely?

Looking at cxl_get_poison_by_endpoint() which iterates over the decoders:

int cxl_get_poison_by_endpoint(struct cxl_port *port)
{
	...
	rc = device_for_each_child(&port->dev, &ctx, poison_by_decoder);
	if (rc < 0)
		return rc;
	...
}

If a decoder lacks a partition and returns -ENODEV, this aborts the
device_for_each_child() loop. Should this return 0 instead of -ENODEV to
allow poison collection to continue for other valid decoders on the device?

>  
>  	cxlmd = cxled_to_memdev(cxled);
>  	cxlds = cxlmd->cxlds;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260826014508.9989-1-icheng@nvidia.com?part=6

[PATCH v6 7/7] cxl/fwctl: Propagate feature RPC delivery errors

[Richard Cheng]

FWCTL_RPC requires delivery failures to be returned as ioctl errors,
while device errors are reported in the output. Get and Set Feature
instead converted all failures into normal responses, sometimes with a
SUCCESS device status.

Initialize the return code to SUCCESS. When the helper fails without a
device error code, return its errno. Continue reporting actual device
errors through rpc_out->retval.

Fixes: 5908f3ed6dc2 ("cxl: Add support to handle user feature commands for get feature")
Fixes: eb5dfcb9e36d ("cxl: Add support to handle user feature commands for set feature")
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
Changelog:

v1 -> v2:
	- Remove redundant CXL_MBOX_CMD_RC_SUCCESS assignments. (Dave Jiang)

---
 drivers/cxl/core/features.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/cxl/core/features.c b/drivers/cxl/core/features.c
index 8d44ce829497..28b326df3398 100644
--- a/drivers/cxl/core/features.c
+++ b/drivers/cxl/core/features.c
@@ -232,7 +232,7 @@ ssize_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
 	int rc;
 
 	if (return_code)
-		*return_code = CXL_MBOX_CMD_RC_INPUT;
+		*return_code = CXL_MBOX_CMD_RC_SUCCESS;
 
 	if (!feat_out || !feat_out_size)
 		return -EINVAL;
@@ -267,9 +267,6 @@ ssize_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
 		data_rcvd_size += mbox_cmd.size_out;
 	} while (data_rcvd_size < feat_out_size);
 
-	if (return_code)
-		*return_code = CXL_MBOX_CMD_RC_SUCCESS;
-
 	return data_rcvd_size;
 }
 
@@ -289,7 +286,7 @@ int cxl_set_feature(struct cxl_mailbox *cxl_mbox,
 	size_t hdr_size;
 
 	if (return_code)
-		*return_code = CXL_MBOX_CMD_RC_INPUT;
+		*return_code = CXL_MBOX_CMD_RC_SUCCESS;
 
 	if (feat_data_size > U16_MAX - offset)
 		return -EINVAL;
@@ -341,8 +338,6 @@ int cxl_set_feature(struct cxl_mailbox *cxl_mbox,
 
 		data_sent_size += data_in_size;
 		if (data_sent_size >= feat_data_size) {
-			if (return_code)
-				*return_code = CXL_MBOX_CMD_RC_SUCCESS;
 			return 0;
 		}
 
@@ -492,6 +487,9 @@ static void *cxlctl_get_feature(struct cxl_features_state *cxlfs,
 	data_size = cxl_get_feature(cxl_mbox, &feat_in->uuid,
 				    feat_in->selection, rpc_out->payload,
 				    count, offset, &return_code);
+	if (data_size < 0 &&
+	    return_code == CXL_MBOX_CMD_RC_SUCCESS)
+		return ERR_PTR(data_size);
 	*out_len = sizeof(struct fwctl_rpc_cxl_out);
 	if (data_size <= 0) {
 		rpc_out->size = 0;
@@ -544,6 +542,8 @@ static void *cxlctl_set_feature(struct cxl_features_state *cxlfs,
 	rc = cxl_set_feature(cxl_mbox, &feat_in->uuid,
 			     feat_in->version, feat_in->feat_data,
 			     data_size, flags, offset, &return_code);
+	if (rc && return_code == CXL_MBOX_CMD_RC_SUCCESS)
+		return ERR_PTR(rc);
 	*out_len = sizeof(*rpc_out);
 	if (rc) {
 		rpc_out->retval = return_code;
-- 
2.43.0