[PATCH v2 59/63] can: flexcan: Use struct_group() to zero struct flexcan_regs regions

Kees Cook
2021-08-18T06:12:44Z

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark both regions of struct flexcan_regs that get
initialized to zero. Avoid the future warnings:

In function 'fortify_memset_chk',
inlined from 'memset_io' at ./include/asm-generic/io.h:1169:2,
inlined from 'flexcan_ram_init' at drivers/net/can/flexcan.c:1403:2:
./include/linux/fortify-string.h:199:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
199 | __write_overflow_field(p_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function 'fortify_memset_chk',
inlined from 'memset_io' at ./include/asm-generic/io.h:1169:2,
inlined from 'flexcan_ram_init' at drivers/net/can/flexcan.c:1408:3:
./include/linux/fortify-string.h:199:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
199 | __write_overflow_field(p_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/net/can/flexcan.c | 68 +++++++++++++++++++--------------------
1 file changed, 34 insertions(+), 34 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 7734229aa078..12b60ad95b02 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -290,31 +290,33 @@ struct flexcan_regs {
u32 dbg1; /* 0x58 */
u32 dbg2; /* 0x5c */
u32 _reserved3[8]; /* 0x60 */
- u8 mb[2][512]; /* 0x80 - Not affected by Soft Reset */
- /* FIFO-mode:
- * MB
- * 0x080...0x08f 0 RX message buffer
- * 0x090...0x0df 1-5 reserved
- * 0x0e0...0x0ff 6-7 8 entry ID table
- * (mx25, mx28, mx35, mx53)
- * 0x0e0...0x2df 6-7..37 8..128 entry ID table
- * size conf'ed via ctrl2::RFFN
- * (mx6, vf610)
- */
- u32 _reserved4[256]; /* 0x480 */
- u32 rximr[64]; /* 0x880 - Not affected by Soft Reset */
- u32 _reserved5[24]; /* 0x980 */
- u32 gfwr_mx6; /* 0x9e0 - MX6 */
- u32 _reserved6[39]; /* 0x9e4 */
- u32 _rxfir[6]; /* 0xa80 */
- u32 _reserved8[2]; /* 0xa98 */
- u32 _rxmgmask; /* 0xaa0 */
- u32 _rxfgmask; /* 0xaa4 */
- u32 _rx14mask; /* 0xaa8 */
- u32 _rx15mask; /* 0xaac */
- u32 tx_smb[4]; /* 0xab0 */
- u32 rx_smb0[4]; /* 0xac0 */
- u32 rx_smb1[4]; /* 0xad0 */
+ struct_group(init,
+ u8 mb[2][512]; /* 0x80 - Not affected by Soft Reset */
+ /* FIFO-mode:
+ * MB
+ * 0x080...0x08f 0 RX message buffer
+ * 0x090...0x0df 1-5 reserved
+ * 0x0e0...0x0ff 6-7 8 entry ID table
+ * (mx25, mx28, mx35, mx53)
+ * 0x0e0...0x2df 6-7..37 8..128 entry ID table
+ * size conf'ed via ctrl2::RFFN
+ * (mx6, vf610)
+ */
+ u32 _reserved4[256]; /* 0x480 */
+ u32 rximr[64]; /* 0x880 - Not affected by Soft Reset */
+ u32 _reserved5[24]; /* 0x980 */
+ u32 gfwr_mx6; /* 0x9e0 - MX6 */
+ u32 _reserved6[39]; /* 0x9e4 */
+ u32 _rxfir[6]; /* 0xa80 */
+ u32 _reserved8[2]; /* 0xa98 */
+ u32 _rxmgmask; /* 0xaa0 */
+ u32 _rxfgmask; /* 0xaa4 */
+ u32 _rx14mask; /* 0xaa8 */
+ u32 _rx15mask; /* 0xaac */
+ u32 tx_smb[4]; /* 0xab0 */
+ u32 rx_smb0[4]; /* 0xac0 */
+ u32 rx_smb1[4]; /* 0xad0 */
+ );
u32 mecr; /* 0xae0 */
u32 erriar; /* 0xae4 */
u32 erridpr; /* 0xae8 */
@@ -328,9 +330,11 @@ struct flexcan_regs {
u32 fdcbt; /* 0xc04 - Not affected by Soft Reset */
u32 fdcrc; /* 0xc08 */
u32 _reserved9[199]; /* 0xc0c */
- u32 tx_smb_fd[18]; /* 0xf28 */
- u32 rx_smb0_fd[18]; /* 0xf70 */
- u32 rx_smb1_fd[18]; /* 0xfb8 */
+ struct_group(init_fd,
+ u32 tx_smb_fd[18]; /* 0xf28 */
+ u32 rx_smb0_fd[18]; /* 0xf70 */
+ u32 rx_smb1_fd[18]; /* 0xfb8 */
+ );
};

static_assert(sizeof(struct flexcan_regs) == 0x4 * 18 + 0xfb8);
@@ -1400,14 +1404,10 @@ static void flexcan_ram_init(struct net_device *dev)
reg_ctrl2 |= FLEXCAN_CTRL2_WRMFRZ;
priv->write(reg_ctrl2, &regs->ctrl2);

- memset_io(&regs->mb[0][0], 0,
- offsetof(struct flexcan_regs, rx_smb1[3]) -
- offsetof(struct flexcan_regs, mb[0][0]) + 0x4);
+ memset_io(&regs->init, 0, sizeof(regs->init));

if (priv->can.ctrlmode & CAN_CTRLMODE_FD)
- memset_io(&regs->tx_smb_fd[0], 0,
- offsetof(struct flexcan_regs, rx_smb1_fd[17]) -
- offsetof(struct flexcan_regs, tx_smb_fd[0]) + 0x4);
+ memset_io(&regs->init_fd, 0, sizeof(regs->init_fd));

reg_ctrl2 &= ~FLEXCAN_CTRL2_WRMFRZ;
priv->write(reg_ctrl2, &regs->ctrl2);
--
2.30.2