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Replace one-element array placeholders for alignment and padding with basic type objects #86

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GustavoARSilva opened this issue Jul 15, 2020 · 1 comment
Closed

Replace one-element array placeholders for alignment and padding with basic type objects #86

GustavoARSilva opened this issue Jul 15, 2020 · 1 comment
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[Idiom] fake flexible array [Refactor] 1-element array Conversion away from one-element array

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@GustavoARSilva
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GustavoARSilva commented Jul 15, 2020 •
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It is a common practice to add 'reserved' fields for alignment (or 'pad' fields for padding) in structures, and it is not uncommon to use one-element arrays for this purpose, as can be seen in the structure below.

drivers/tty/tty_io.c:2675:

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];
};

One-element arrays are being deprecated, therefore such reserved fields should be replaced with basic type objects, as follows:

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 5a6f36b391d9..3b6e5ec3ba54 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2683,7 +2683,7 @@ struct serial_struct32 {
         compat_int_t    baud_base;
         unsigned short  close_delay;
         char    io_type;
-        char    reserved_char[1];
+        char    reserved_char;
         compat_int_t    hub6;
         unsigned short  closing_wait; /* time to wait before closing */
         unsigned short  closing_wait2; /* no longer used... */
@@ -2691,7 +2691,7 @@ struct serial_struct32 {
         unsigned short  iomem_reg_shift;
         unsigned int    port_high;
      /* compat_ulong_t  iomap_base FIXME */
-        compat_int_t    reserved[1];
+        compat_int_t    reserved;
 };
 
 static int compat_tty_tiocsserial(struct tty_struct *tty,
@GustavoARSilva GustavoARSilva self-assigned this Jul 15, 2020
@kees kees changed the title Replace one-element array placeholders for a lignment with simple value types Replace one-element array placeholders for alignment with simple value types Jul 15, 2020
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 15, 2020
@GustavoARSilva @intel-lab-lkp
wil6210: Avoid the use of one-element array
64b8cd8 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type 'u8 reserved'[2], once this is just
a placeholder for alignment.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/wil6210-20200715.md
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 16, 2020
@GustavoARSilva @intel-lab-lkp
tty: Avoid the use of one-element arrays
ce95c10 
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] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tty-20200716.md
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 17, 2020
@GustavoARSilva @intel-lab-lkp
ASoC: Intel: Skylake: Avoid the use of one-element array
64b7c5b 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type 'u8 reserved'[2], once it seems this
is just a placeholder for alignment.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/skylake-20200717.md
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 20, 2020
@GustavoARSilva @broonie
ASoC: Intel: Skylake: Avoid the use of one-element array
23f8d96 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type 'u8 reserved'[2], once it seems this
is just a placeholder for alignment.

[1] KSPP#79
[2] KSPP#86

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Tested-by: kernel test robot <[email protected]>
Reviewed-by: Amadeusz Sławiński <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/skylake-20200717.md
Link: https://lore.kernel.org/r/20200717215500.GA13910@embeddedor
Signed-off-by: Mark Brown <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 22, 2020
@GustavoARSilva @intel-lab-lkp
tg3: Avoid the use of one-element array
5ab79c6 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type 'u32 reserved2'[2], once it seems
this is just a placeholder for alignment.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tg3-20200718.md
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 22, 2020
@GustavoARSilva @intel-lab-lkp
bna: bfi.h: Avoid the use of one-element array
26a2344 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type 'u8 rsvd'[2], once it seems this is
just a placeholder for alignment.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/bfi-20200718.md
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 22, 2020
@GustavoARSilva @intel-lab-lkp
tty: Avoid the use of one-element arrays
7f3a4c0 
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] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tty-20200716.md
Acked-by: Jiri Slaby <[email protected]>
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 22, 2020
@GustavoARSilva @intel-lab-lkp
net: qed_hsi.h: Avoid the use of one-element array
d724c63 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type '__le32 reserved1'[2], once it seems
this is just a placeholder for alignment.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/qed_hsi-20200718.md
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Jul 23, 2020
@GustavoARSilva @intel-lab-lkp
tty: Avoid the use of one-element arrays
d19cfc9 
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.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tty-20200716.md
Acked-by: Jiri Slaby <[email protected]>
Signed-off-by: Gustavo A. R. Silva <[email protected]>
ruscur pushed a commit to ruscur/linux that referenced this issue Jul 30, 2020
@GustavoARSilva @gregkh
tty: Avoid the use of one-element arrays
e5b9f4b 
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.

[1] KSPP#79
[2] KSPP#86

Tested-by: kernel test robot <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tty-20200716.md
Acked-by: Jiri Slaby <[email protected]>
Signed-off-by: Gustavo A. R. Silva <[email protected]>
Link: https://lore.kernel.org/r/f49bf0e27eaac396c96d21392c8c284f9f5ef52a.1595543280.git.gustavoars@kernel.org
Signed-off-by: Greg Kroah-Hartman <[email protected]>
kitakar5525 pushed a commit to kitakar5525/linux-kernel that referenced this issue Sep 16, 2020
@GustavoARSilva @cujomalainey
UPSTREAM: ASoC: Intel: Skylake: Avoid the use of one-element array
f0e6d0f 
One-element arrays are being deprecated[1]. Replace the one-element
array with a simple value type 'u8 reserved'[2], once it seems this
is just a placeholder for alignment.

[1] KSPP/linux#79
[2] KSPP/linux#86

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Tested-by: kernel test robot <[email protected]>
Reviewed-by: Amadeusz Sławiński <[email protected]>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/skylake-20200717.md
Link: https://lore.kernel.org/r/20200717215500.GA13910@embeddedor
Signed-off-by: Mark Brown <[email protected]>
(cherry picked from commit 23f8d96)

BUG=b:162008784
TEST=Test audio on volteer.

Signed-off-by: Mike Mason <[email protected]>
@GustavoARSilva GustavoARSilva changed the title Replace one-element array placeholders for alignment with simple value types Replace one-element array placeholders for alignment and padding with simple value types Sep 28, 2020
fengguang pushed a commit to 0day-ci/linux that referenced this issue Sep 29, 2020
@GustavoARSilva @intel-lab-lkp
fddi/skfp: Avoid the use of one-element array
b2882c1 
One-element arrays are being deprecated[1]. Replace the one-element array
with a simple object of type u_char: 'u_char rm_pad1'[2], once it seems
this is just a placeholder for padding.

[1] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[2] KSPP#86

Built-tested-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/lkml/5f72c23f.%2FkPBWcZBu+W6HKH4%[email protected]/
Signed-off-by: Gustavo A. R. Silva <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Sep 30, 2020
@GustavoARSilva @davem330
fddi/skfp: Avoid the use of one-element array
2c956a5 
One-element arrays are being deprecated[1]. Replace the one-element array
with a simple object of type u_char: 'u_char rm_pad1'[2], once it seems
this is just a placeholder for padding.

[1] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[2] KSPP#86

Built-tested-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/lkml/5f72c23f.%2FkPBWcZBu+W6HKH4%[email protected]/
Signed-off-by: Gustavo A. R. Silva <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
fengguang pushed a commit to 0day-ci/linux that referenced this issue Oct 2, 2020
@GustavoARSilva @intel-lab-lkp
block: scsi_ioctl: Avoid the use of one-element arrays
dcb49af 
One-element arrays are being deprecated[1]. Replace the one-element array
with a simple object of type compat_caddr_t: 'compat_caddr_t unused'[2],
once it seems this field is actually never used.

Also, update struct cdrom_generic_command in UAPI by adding an
anonimous union to avoid using the one-element array _reserved_.

[1] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[2] KSPP#86

Build-tested-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/lkml/5f76f5d0.qJ4t%2FHWuRzSW7bTa%[email protected]/
Signed-off-by: Gustavo A. R. Silva <[email protected]>
ruscur pushed a commit to ruscur/linux that referenced this issue Oct 6, 2020
@GustavoARSilva @axboe
block: scsi_ioctl: Avoid the use of one-element arrays
f5ace5e 
One-element arrays are being deprecated[1]. Replace the one-element array
with a simple object of type compat_caddr_t: 'compat_caddr_t unused'[2],
once it seems this field is actually never used.

Also, update struct cdrom_generic_command in UAPI by adding an
anonimous union to avoid using the one-element array _reserved_.

[1] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[2] KSPP#86

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Link: https://lore.kernel.org/lkml/5f76f5d0.qJ4t%2FHWuRzSW7bTa%[email protected]/
Build-tested-by: kernel test robot <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
@GustavoARSilva GustavoARSilva changed the title Replace one-element array placeholders for alignment and padding with simple value types Replace one-element array placeholders for alignment and padding with basic type objects Jun 10, 2021
@kees kees mentioned this issue Sep 16, 2021
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kees commented Feb 6, 2024

I think with -fstrict-flex-arrays=3, we can safely ignore this now. If it's not being used as a flexible array, it will be handled sanely now.

@kees kees closed this as completed Feb 6, 2024
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