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| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-03-09 13:08:13 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2020-03-14 14:43:13 -0400 |
| commit | 47b1030612f4382a976be6aa2369cf5d973ca154 (patch) | |
| tree | 938a12f51a7ea97c4714e3b9fc36b1d6d2312e84 | |
| parent | e32ac2459cdac01f9b177eed526a3ffa1797039d (diff) | |
| download | linux-47b1030612f4382a976be6aa2369cf5d973ca154.tar.bz2 | |
ext4: use flexible-array member for xattr structs
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>
Link: https://lore.kernel.org/r/20200309180813.GA3347@embeddedor
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | fs/ext4/xattr.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h index f39cad2abe2a..ffe21ac77f78 100644 --- a/fs/ext4/xattr.h +++ b/fs/ext4/xattr.h @@ -48,7 +48,7 @@ struct ext4_xattr_entry { __le32 e_value_inum; /* inode in which the value is stored */ __le32 e_value_size; /* size of attribute value */ __le32 e_hash; /* hash value of name and value */ - char e_name[0]; /* attribute name */ + char e_name[]; /* attribute name */ }; #define EXT4_XATTR_PAD_BITS 2 @@ -118,7 +118,7 @@ struct ext4_xattr_ibody_find { struct ext4_xattr_inode_array { unsigned int count; /* # of used items in the array */ - struct inode *inodes[0]; + struct inode *inodes[]; }; extern const struct xattr_handler ext4_xattr_user_handler; |