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authorGustavo A. R. Silva <gustavo@embeddedor.com>2020-04-01 21:03:55 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-02 09:35:25 -0700
commit8cb92435e2fdd044d6e6e3a47eb761f0d024eb85 (patch)
tree572896cf39c2ba83d77a7dadfba09ff0202b8129 /fs/ocfs2
parentfa803cf8f39feba691732a78e47797c5dc388ba2 (diff)
ocfs2: dlm: 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://urldefense.com/v3/__https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html__;!!GqivPVa7Brio!OVOYL_CouISa5L1Lw-20EEFQntw6cKMx-j8UdY4z78uYgzKBUFcfpn50GaurvbV5v7YiUA$ [2] https://urldefense.com/v3/__https://github.com/KSPP/linux/issues/21__;!!GqivPVa7Brio!OVOYL_CouISa5L1Lw-20EEFQntw6cKMx-j8UdY4z78uYgzKBUFcfpn50GaurvbXs8Eh8eg$ [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Mark Fasheh <mark@fasheh.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Junxiao Bi <junxiao.bi@oracle.com> Cc: Changwei Ge <gechangwei@live.cn> Cc: Gang He <ghe@suse.com> Cc: Jun Piao <piaojun@huawei.com> Link: http://lkml.kernel.org/r/20200309202016.GA8210@embeddedor Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/ocfs2')
-rw-r--r--fs/ocfs2/dlm/dlmcommon.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
index 0463dce65bb2..c8a444622faa 100644
--- a/fs/ocfs2/dlm/dlmcommon.h
+++ b/fs/ocfs2/dlm/dlmcommon.h
@@ -564,7 +564,7 @@ struct dlm_migratable_lockres
// 48 bytes
u8 lvb[DLM_LVB_LEN];
// 112 bytes
- struct dlm_migratable_lock ml[0]; // 16 bytes each, begins at byte 112
+ struct dlm_migratable_lock ml[]; // 16 bytes each, begins at byte 112
};
#define DLM_MIG_LOCKRES_MAX_LEN \
(sizeof(struct dlm_migratable_lockres) + \
@@ -601,7 +601,7 @@ struct dlm_convert_lock
u8 name[O2NM_MAX_NAME_LEN];
- s8 lvb[0];
+ s8 lvb[];
};
#define DLM_CONVERT_LOCK_MAX_LEN (sizeof(struct dlm_convert_lock)+DLM_LVB_LEN)
@@ -616,7 +616,7 @@ struct dlm_unlock_lock
u8 name[O2NM_MAX_NAME_LEN];
- s8 lvb[0];
+ s8 lvb[];
};
#define DLM_UNLOCK_LOCK_MAX_LEN (sizeof(struct dlm_unlock_lock)+DLM_LVB_LEN)
@@ -632,7 +632,7 @@ struct dlm_proxy_ast
u8 name[O2NM_MAX_NAME_LEN];
- s8 lvb[0];
+ s8 lvb[];
};
#define DLM_PROXY_AST_MAX_LEN (sizeof(struct dlm_proxy_ast)+DLM_LVB_LEN)