[PATCH net] net/mlx5: Fix MCIA register buffer overflow on 32 dword reads

[PATCH net] net/mlx5: Fix MCIA register buffer overflow on 32 dword reads

[Tariq Toukan]

From: Gal Pressman <gal@nvidia.com>

The MCIA register can return up to 32 dwords (128 bytes) when the device
advertises the mcia_32dwords capability, but struct
mlx5_ifc_mcia_reg_bits only defines dword_0..11, leaving room for just
12 dwords (48 bytes) of data.

mlx5_query_mcia() clamps the read size to mlx5_mcia_max_bytes() and then
memcpy()s that many bytes out of the register, potentially reading past
the end of the 'out' buffer. On kernels built with FORTIFY_SOURCE this
is caught as a buffer overflow while reading the module EEPROM via
ethtool:

  detected buffer overflow in memcpy
  kernel BUG at lib/string_helpers.c:1048!
  RIP: 0010:fortify_panic+0x13/0x20
  Call Trace:
   mlx5_query_mcia.isra.0+0x200/0x210 [mlx5_core]
   mlx5_query_module_eeprom_by_page+0x4a/0xa0 [mlx5_core]
   mlx5e_get_module_eeprom_by_page+0xbb/0x120 [mlx5_core]
   eeprom_prepare_data+0xf3/0x170
   ethnl_default_doit+0xf1/0x3b0

Extend the mcia_reg layout to 32 dwords.

Fixes: 271907ee2f29 ("net/mlx5: Query the maximum MCIA register read size from firmware")
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Alex Lazar <alazar@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/port.c |  4 ++--
 include/linux/mlx5/mlx5_ifc.h                  | 13 +------------
 2 files changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/port.c b/drivers/net/ethernet/mellanox/mlx5/core/port.c
index ddbe9ca8971d..9f682f6bdb50 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/port.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/port.c
@@ -314,7 +314,7 @@ static int mlx5_query_module_id(struct mlx5_core_dev *dev, int module_num,
 		return -EIO;
 	}
 
-	ptr = MLX5_ADDR_OF(mcia_reg, out, dword_0);
+	ptr = MLX5_ADDR_OF(mcia_reg, out, dwords);
 
 	*module_id = ptr[0];
 
@@ -399,7 +399,7 @@ static int mlx5_query_mcia(struct mlx5_core_dev *dev,
 		return -EIO;
 	}
 
-	ptr = MLX5_ADDR_OF(mcia_reg, out, dword_0);
+	ptr = MLX5_ADDR_OF(mcia_reg, out, dwords);
 	memcpy(data, ptr, size);
 
 	return size;
diff --git a/include/linux/mlx5/mlx5_ifc.h b/include/linux/mlx5/mlx5_ifc.h
index 695c86ee6d7a..8f18a508320d 100644
--- a/include/linux/mlx5/mlx5_ifc.h
+++ b/include/linux/mlx5/mlx5_ifc.h
@@ -12215,18 +12215,7 @@ struct mlx5_ifc_mcia_reg_bits {
 
 	u8         reserved_at_60[0x20];
 
-	u8         dword_0[0x20];
-	u8         dword_1[0x20];
-	u8         dword_2[0x20];
-	u8         dword_3[0x20];
-	u8         dword_4[0x20];
-	u8         dword_5[0x20];
-	u8         dword_6[0x20];
-	u8         dword_7[0x20];
-	u8         dword_8[0x20];
-	u8         dword_9[0x20];
-	u8         dword_10[0x20];
-	u8         dword_11[0x20];
+	u8         dwords[0x400];
 };
 
 struct mlx5_ifc_dcbx_param_bits {

base-commit: 3f1f755366687d051174739fb99f7d560202f60b
-- 
2.44.0