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Message-ID: <20200226221804.GA8564@embeddedor>
Date: Wed, 26 Feb 2020 16:18:04 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Alasdair Kergon <agk@...hat.com>,
Mike Snitzer <snitzer@...hat.com>,
"dm-devel@...hat.comSong Liu" <song@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
"Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH][next] md: Replace zero-length array with flexible-array
member
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
drivers/md/dm-crypt.c | 2 +-
drivers/md/dm-integrity.c | 2 +-
drivers/md/dm-log-writes.c | 2 +-
drivers/md/dm-raid.c | 2 +-
drivers/md/dm-raid1.c | 2 +-
drivers/md/dm-stats.c | 2 +-
drivers/md/dm-stripe.c | 2 +-
drivers/md/dm-switch.c | 2 +-
drivers/md/md-linear.h | 2 +-
drivers/md/persistent-data/dm-btree-internal.h | 2 +-
drivers/md/raid1.h | 2 +-
drivers/md/raid10.h | 2 +-
12 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 1c641efeeca7..bea260a82a2a 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -212,7 +212,7 @@ struct crypt_config {
struct mutex bio_alloc_lock;
u8 *authenc_key; /* space for keys in authenc() format (if used) */
- u8 key[0];
+ u8 key[];
};
#define MIN_IOS 64
diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index b225b3e445fa..e22e6d65862a 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -89,7 +89,7 @@ struct journal_entry {
} s;
__u64 sector;
} u;
- commit_id_t last_bytes[0];
+ commit_id_t last_bytes[];
/* __u8 tag[0]; */
};
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index 99721c76225d..9e21df5bb998 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -127,7 +127,7 @@ struct pending_block {
char *data;
u32 datalen;
struct list_head list;
- struct bio_vec vecs[0];
+ struct bio_vec vecs[];
};
struct per_bio_data {
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 9a18bef0a5ff..10e8b2fe787b 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -254,7 +254,7 @@ struct raid_set {
int mode;
} journal_dev;
- struct raid_dev dev[0];
+ struct raid_dev dev[];
};
static void rs_config_backup(struct raid_set *rs, struct rs_layout *l)
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 089aed57e083..2f655d9f4200 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -83,7 +83,7 @@ struct mirror_set {
struct work_struct trigger_event;
unsigned nr_mirrors;
- struct mirror mirror[0];
+ struct mirror mirror[];
};
DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle,
diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 71417048256a..35d368c418d0 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -56,7 +56,7 @@ struct dm_stat {
size_t percpu_alloc_size;
size_t histogram_alloc_size;
struct dm_stat_percpu *stat_percpu[NR_CPUS];
- struct dm_stat_shared stat_shared[0];
+ struct dm_stat_shared stat_shared[];
};
#define STAT_PRECISE_TIMESTAMPS 1
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 63bbcc20f49a..51fbfcf8efa1 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -41,7 +41,7 @@ struct stripe_c {
/* Work struct used for triggering events*/
struct work_struct trigger_event;
- struct stripe stripe[0];
+ struct stripe stripe[];
};
/*
diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
index 8a0f057b8122..bff4c7fa1cd2 100644
--- a/drivers/md/dm-switch.c
+++ b/drivers/md/dm-switch.c
@@ -53,7 +53,7 @@ struct switch_ctx {
/*
* Array of dm devices to switch between.
*/
- struct switch_path path_list[0];
+ struct switch_path path_list[];
};
static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
diff --git a/drivers/md/md-linear.h b/drivers/md/md-linear.h
index 8381d651d4ed..24e97db50ebb 100644
--- a/drivers/md/md-linear.h
+++ b/drivers/md/md-linear.h
@@ -12,6 +12,6 @@ struct linear_conf
struct rcu_head rcu;
sector_t array_sectors;
int raid_disks; /* a copy of mddev->raid_disks */
- struct dev_info disks[0];
+ struct dev_info disks[];
};
#endif
diff --git a/drivers/md/persistent-data/dm-btree-internal.h b/drivers/md/persistent-data/dm-btree-internal.h
index a240990a7f33..f4e644dd8101 100644
--- a/drivers/md/persistent-data/dm-btree-internal.h
+++ b/drivers/md/persistent-data/dm-btree-internal.h
@@ -38,7 +38,7 @@ struct node_header {
struct btree_node {
struct node_header header;
- __le64 keys[0];
+ __le64 keys[];
} __packed;
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
index e7ccad898736..b7eb09e8c025 100644
--- a/drivers/md/raid1.h
+++ b/drivers/md/raid1.h
@@ -180,7 +180,7 @@ struct r1bio {
* if the IO is in WRITE direction, then multiple bios are used.
* We choose the number when they are allocated.
*/
- struct bio *bios[0];
+ struct bio *bios[];
/* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/
};
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index d3eaaf3eb1bc..79cd2b7d3128 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -153,7 +153,7 @@ struct r10bio {
};
sector_t addr;
int devnum;
- } devs[0];
+ } devs[];
};
/* bits for r10bio.state */
--
2.25.0
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