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| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-03-09 19:23:08 +0100 |
|---|---|---|
| committer | Dave Kleikamp <dave.kleikamp@oracle.com> | 2020-03-09 21:18:51 +0100 |
| commit | 7aba5dcc234635b44b2781dbc268048cfba388ad (patch) | |
| tree | 2bf56f3cfe58a7086d072113f004197c0b013cac /fs/jfs | |
| parent | Linux 5.6-rc5 (diff) | |
| download | linux-7aba5dcc234635b44b2781dbc268048cfba388ad.tar.xz linux-7aba5dcc234635b44b2781dbc268048cfba388ad.zip | |
jfs: 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@embeddedor.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Diffstat (limited to 'fs/jfs')
| -rw-r--r-- | fs/jfs/jfs_dtree.c | 2 | ||||
| -rw-r--r-- | fs/jfs/jfs_xattr.h | 4 |
2 files changed, 3 insertions, 3 deletions
diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c index 3acc954f7c04..837d42f61464 100644 --- a/fs/jfs/jfs_dtree.c +++ b/fs/jfs/jfs_dtree.c @@ -2964,7 +2964,7 @@ struct jfs_dirent { loff_t position; int ino; u16 name_len; - char name[0]; + char name[]; }; /* diff --git a/fs/jfs/jfs_xattr.h b/fs/jfs/jfs_xattr.h index f0558b3348da..c50167a7bc50 100644 --- a/fs/jfs/jfs_xattr.h +++ b/fs/jfs/jfs_xattr.h @@ -17,12 +17,12 @@ struct jfs_ea { u8 flag; /* Unused? */ u8 namelen; /* Length of name */ __le16 valuelen; /* Length of value */ - char name[0]; /* Attribute name (includes null-terminator) */ + char name[]; /* Attribute name (includes null-terminator) */ }; /* Value immediately follows name */ struct jfs_ea_list { __le32 size; /* overall size */ - struct jfs_ea ea[0]; /* Variable length list */ + struct jfs_ea ea[]; /* Variable length list */ }; /* Macros for defining maxiumum number of bytes supported for EAs */ |