[PATCH RESEND][next] net: fddi: skfp: smt: Replace one-element array with flexible-array member
From: Gustavo A. R. Silva
Date: Wed Mar 10 2021 - 00:31:08 EST
There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].
Refactor the code according to the use of flexible-array members in
smt_sif_operation structure, instead of one-element arrays. Also, make
use of the struct_size() helper instead of the open-coded version
to calculate the size of the struct-with-flex-array. Additionally, make
use of the typeof operator to properly determine the object type to be
passed to macro smtod().
Also, this helps the ongoing efforts to enable -Warray-bounds by fixing
the following warnings:
CC [M] drivers/net/fddi/skfp/smt.o
drivers/net/fddi/skfp/smt.c: In function ‘smt_send_sif_operation’:
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
| ^~~
drivers/net/fddi/skfp/smt.c:1084:30: warning: array subscript 1 is above array bounds of ‘struct smt_p_lem[1]’ [-Warray-bounds]
1084 | smt_fill_lem(smc,&sif->lem[i],i) ;
| ~~~~~~~~^~~
In file included from drivers/net/fddi/skfp/h/smc.h:42,
from drivers/net/fddi/skfp/smt.c:15:
drivers/net/fddi/skfp/h/smt.h:767:19: note: while referencing ‘lem’
767 | struct smt_p_lem lem[1] ; /* phy lem status */
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
Changes in RESEND:
- None. Resending now that net-next is open.
drivers/net/fddi/skfp/h/smt.h | 4 +---
drivers/net/fddi/skfp/smt.c | 4 ++--
2 files changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/net/fddi/skfp/h/smt.h b/drivers/net/fddi/skfp/h/smt.h
index a0dbc0f57a55..751b5bb87a9d 100644
--- a/drivers/net/fddi/skfp/h/smt.h
+++ b/drivers/net/fddi/skfp/h/smt.h
@@ -764,10 +764,8 @@ struct smt_sif_operation {
struct smt_p_setcount setcount ; /* Set Count mandatory */
#endif
/* must be last */
- struct smt_p_lem lem[1] ; /* phy lem status */
+ struct smt_p_lem lem[]; /* phy lem status */
} ;
-#define SIZEOF_SMT_SIF_OPERATION (sizeof(struct smt_sif_operation)- \
- sizeof(struct smt_p_lem))
/*
* ECF : echo frame
diff --git a/drivers/net/fddi/skfp/smt.c b/drivers/net/fddi/skfp/smt.c
index 774a6e3b0a67..6b68a53f1b38 100644
--- a/drivers/net/fddi/skfp/smt.c
+++ b/drivers/net/fddi/skfp/smt.c
@@ -1063,9 +1063,9 @@ static void smt_send_sif_operation(struct s_smc *smc, struct fddi_addr *dest,
#endif
if (!(mb = smt_build_frame(smc,SMT_SIF_OPER,SMT_REPLY,
- SIZEOF_SMT_SIF_OPERATION+ports*sizeof(struct smt_p_lem))))
+ struct_size(sif, lem, ports))))
return ;
- sif = smtod(mb, struct smt_sif_operation *) ;
+ sif = smtod(mb, typeof(sif));
smt_fill_timestamp(smc,&sif->ts) ; /* set time stamp */
smt_fill_mac_status(smc,&sif->status) ; /* set mac status */
smt_fill_mac_counter(smc,&sif->mc) ; /* set mac counter field */
--
2.27.0