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Subject[PATCH v2][next] tty: Avoid the use of one-element arrays
One-element arrays are being deprecated[1]. Replace the one-element arrays
with simple value types 'char reserved_char' and 'compat_int_t reserved'[2],
once it seems these are just placeholders for alignment.

Also, while there, use the preferred form for passing a size of a struct.
The alternative form where struct name is spelled out hurts readability
and introduces an opportunity for a bug when the variable type is changed
but the corresponding sizeof that is passed as argument is not.

Lastly, fix the checkpatch.pl warnings below:

ERROR: code indent should use tabs where possible
+ char reserved_char;$

WARNING: please, no spaces at the start of a line
+ char reserved_char;$

ERROR: code indent should use tabs where possible
+ compat_int_t reserved;$

WARNING: please, no spaces at the start of a line
+ compat_int_t reserved;$

[1] https://github.com/KSPP/linux/issues/79
[2] https://github.com/KSPP/linux/issues/86

Tested-by: kernel test robot <lkp@intel.com>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tty-20200716.md
Acked-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
- Fix indentation issues in struct serial_struct32.
- Add Jiri's Acked-by.

drivers/tty/tty_io.c | 42 +++++++++++++++++++++---------------------
1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 5a6f36b391d9..bb74c2ffcced 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2673,25 +2673,25 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
#ifdef CONFIG_COMPAT

struct serial_struct32 {
- compat_int_t type;
- compat_int_t line;
- compat_uint_t port;
- compat_int_t irq;
- compat_int_t flags;
- compat_int_t xmit_fifo_size;
- compat_int_t custom_divisor;
- compat_int_t baud_base;
- unsigned short close_delay;
- char io_type;
- char reserved_char[1];
- compat_int_t hub6;
- unsigned short closing_wait; /* time to wait before closing */
- unsigned short closing_wait2; /* no longer used... */
- compat_uint_t iomem_base;
- unsigned short iomem_reg_shift;
- unsigned int port_high;
- /* compat_ulong_t iomap_base FIXME */
- compat_int_t reserved[1];
+ compat_int_t type;
+ compat_int_t line;
+ compat_uint_t port;
+ compat_int_t irq;
+ compat_int_t flags;
+ compat_int_t xmit_fifo_size;
+ compat_int_t custom_divisor;
+ compat_int_t baud_base;
+ unsigned short close_delay;
+ char io_type;
+ char reserved_char;
+ compat_int_t hub6;
+ unsigned short closing_wait; /* time to wait before closing */
+ unsigned short closing_wait2; /* no longer used... */
+ compat_uint_t iomem_base;
+ unsigned short iomem_reg_shift;
+ unsigned int port_high;
+ /* compat_ulong_t iomap_base FIXME */
+ compat_int_t reserved;
};

static int compat_tty_tiocsserial(struct tty_struct *tty,
@@ -2705,7 +2705,7 @@ static int compat_tty_tiocsserial(struct tty_struct *tty,
struct serial_struct v;
int flags;

- if (copy_from_user(&v32, ss, sizeof(struct serial_struct32)))
+ if (copy_from_user(&v32, ss, sizeof(*ss)))
return -EFAULT;

memcpy(&v, &v32, offsetof(struct serial_struct32, iomem_base));
@@ -2743,7 +2743,7 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
0xfffffff : ptr_to_compat(v.iomem_base);
v32.iomem_reg_shift = v.iomem_reg_shift;
v32.port_high = v.port_high;
- if (copy_to_user(ss, &v32, sizeof(struct serial_struct32)))
+ if (copy_to_user(ss, &v32, sizeof(v32)))
err = -EFAULT;
}
return err;
--
2.27.0
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