| Message ID | 20200309182442.GA5422@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [next] nfs: Replace zero-length array with flexible-array member | expand |
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index d4b839b6cf89..a551a30047f9 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -141,7 +141,7 @@ struct nfs_cache_array { int size; int eof_index; u64 last_cookie; - struct nfs_cache_array_entry array[0]; + struct nfs_cache_array_entry array[]; }; typedef int (*decode_dirent_t)(struct xdr_stream *, struct nfs_entry *, bool); diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 69b7ab7a5815..cc0960558284 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -5550,7 +5550,7 @@ static int buf_to_pages_noslab(const void *buf, size_t buflen, struct nfs4_cached_acl { int cached; size_t len; - char data[0]; + char data[]; }; static void nfs4_set_cached_acl(struct inode *inode, struct nfs4_cached_acl *acl)
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@embeddedor.com> --- fs/nfs/dir.c | 2 +- fs/nfs/nfs4proc.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)