[PATCH AUTOSEL 5.15 27/33] software node: Correct a OOB check in software_node_get_reference_args()

[Sasha Levin <sashal@kernel.org>]

From: Zijun Hu <quic_zijuhu@quicinc.com>

[ Upstream commit 31e4e12e0e9609850cefd4b2e1adf782f56337d6 ]

software_node_get_reference_args() wants to get @index-th element, so
the property value requires at least '(index + 1) * sizeof(*ref)' bytes
but that can not be guaranteed by current OOB check, and may cause OOB
for malformed property.

Fix by using as OOB check '((index + 1) * sizeof(*ref) > prop->length)'.

Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Link: https://lore.kernel.org/r/20250414-fix_swnode-v2-1-9c9e6ae11eab@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

## Final Decision **YES** This commit should be backported to stable
kernel trees. **Extensive Explanation:** 1. **Critical Security Fix**:
This commit fixes a clear out-of-bounds memory access vulnerability in
`software_node_get_reference_args()` at line 532 in
`/drivers/base/swnode.c`. The original bounds check `index
capability_test capability_test.c f2fs_folio_analysis.md
ipv4_multipath_analysis.md ipv6_route_allocation_rcu_analysis.md
ixgbe_e610_set_phys_id_analysis.md linux lpfc_timeout_analysis.md
mac80211_mlo_mbssid_analysis.md pfcp_driver_historical_analysis.md
rtl_bb_delay_analysis.md rtw89_mlo_analysis.md
tcp_multipath_load_balance_analysis.md test_unaligned_diff
test_unaligned_diff.c type_size_check type_size_check.c
veth_driver_analysis.md wifi_mlo_mbssid_tx_link_id_analysis.md
sizeof(*ref) >= prop->length` has an off-by-one error that allows
reading beyond allocated memory when accessing `ref_array[index]`. 2.
**Vulnerability Details**: The bug allows an attacker to read kernel
memory beyond the allocated property buffer. To access
`ref_array[index]`, the code needs `(index + 1) capability_test
capability_test.c f2fs_folio_analysis.md ipv4_multipath_analysis.md
ipv6_route_allocation_rcu_analysis.md ixgbe_e610_set_phys_id_analysis.md
linux lpfc_timeout_analysis.md mac80211_mlo_mbssid_analysis.md
pfcp_driver_historical_analysis.md rtl_bb_delay_analysis.md
rtw89_mlo_analysis.md tcp_multipath_load_balance_analysis.md
test_unaligned_diff test_unaligned_diff.c type_size_check
type_size_check.c veth_driver_analysis.md
wifi_mlo_mbssid_tx_link_id_analysis.md sizeof(*ref)` bytes, but the
original check only ensures `index capability_test capability_test.c
f2fs_folio_analysis.md ipv4_multipath_analysis.md
ipv6_route_allocation_rcu_analysis.md ixgbe_e610_set_phys_id_analysis.md
linux lpfc_timeout_analysis.md mac80211_mlo_mbssid_analysis.md
pfcp_driver_historical_analysis.md rtl_bb_delay_analysis.md
rtw89_mlo_analysis.md tcp_multipath_load_balance_analysis.md
test_unaligned_diff test_unaligned_diff.c type_size_check
type_size_check.c veth_driver_analysis.md
wifi_mlo_mbssid_tx_link_id_analysis.md sizeof(*ref)` bytes are
available. This creates a window where `index capability_test
capability_test.c f2fs_folio_analysis.md ipv4_multipath_analysis.md
ipv6_route_allocation_rcu_analysis.md ixgbe_e610_set_phys_id_analysis.md
linux lpfc_timeout_analysis.md mac80211_mlo_mbssid_analysis.md
pfcp_driver_historical_analysis.md rtl_bb_delay_analysis.md
rtw89_mlo_analysis.md tcp_multipath_load_balance_analysis.md
test_unaligned_diff test_unaligned_diff.c type_size_check
type_size_check.c veth_driver_analysis.md
wifi_mlo_mbssid_tx_link_id_analysis.md sizeof(*ref) < prop->length` but
`(index + 1) capability_test capability_test.c f2fs_folio_analysis.md
ipv4_multipath_analysis.md ipv6_route_allocation_rcu_analysis.md
ixgbe_e610_set_phys_id_analysis.md linux lpfc_timeout_analysis.md
mac80211_mlo_mbssid_analysis.md pfcp_driver_historical_analysis.md
rtl_bb_delay_analysis.md rtw89_mlo_analysis.md
tcp_multipath_load_balance_analysis.md test_unaligned_diff
test_unaligned_diff.c type_size_check type_size_check.c
veth_driver_analysis.md wifi_mlo_mbssid_tx_link_id_analysis.md
sizeof(*ref) > prop->length`, allowing out-of-bounds access. 3.
**Security Impact**: This vulnerability can lead to: - Information
disclosure through kernel memory leaks - Potential system crashes from
invalid memory access - Exploitation through malformed device tree
properties 4. **Perfect Backport Candidate**: - **Minimal code change**:
Single line fix changing `>=` to `>` and adding `+ 1` - **No feature
additions**: Pure bug fix with no new functionality - **Low regression
risk**: Makes bounds checking more restrictive, safer - **Core
infrastructure**: Affects fundamental device property framework used
across many drivers 5. **Historical Precedent**: The provided similar
commits show a clear pattern - other defensive programming fixes in the
same `software_node` subsystem (commits #1, #2, and #4) were all marked
as suitable for backporting. This commit follows the same pattern of
fixing potential memory safety issues with minimal, targeted changes. 6.
**Maintainer Review**: The commit has been reviewed by Sakari Ailus,
indicating community confidence in the fix. 7. **Stable Tree
Compliance**: Meets all stable tree criteria - fixes important bug,
minimal risk, contained change, no architectural modifications, and
addresses a security vulnerability in critical kernel infrastructure.
The commit represents exactly the type of fix that stable trees are
designed to accommodate: a small, well-reviewed security fix that
prevents potential exploitation without introducing new risks.

 drivers/base/swnode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 15f149fc19401..0af6071f86641 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -524,7 +524,7 @@ software_node_get_reference_args(const struct fwnode_handle *fwnode,
 	if (prop->is_inline)
 		return -EINVAL;
 
-	if (index * sizeof(*ref) >= prop->length)
+	if ((index + 1) * sizeof(*ref) > prop->length)
 		return -ENOENT;
 
 	ref_array = prop->pointer;
-- 
2.39.5