Commit c92a08c1 authored Jul 31, 2021 by Kees Cook

can: flexcan: Use struct_group() to zero struct flexcan_regs regions



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: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Kees Cook <keescook@chromium.org>

parent 69dae0fe

drivers/net/can/flexcan.c

+34 −34

Original line number	Diff line number	Diff line
		@@ -290,6 +290,7 @@ struct flexcan_regs {
		u32 dbg1; /* 0x58 */
		u32 dbg2; /* 0x5c */
		u32 _reserved3[8]; /* 0x60 */
		struct_group(init,
		u8 mb[2][512]; /* 0x80 - Not affected by Soft Reset */
		/* FIFO-mode:
		* MB
		@@ -315,6 +316,7 @@ struct flexcan_regs {
		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 */
		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);