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authorGustavo A. R. Silva <gustavo@embeddedor.com>2020-03-09 21:08:13 +0300
committerTheodore Ts'o <tytso@mit.edu>2020-03-14 21:43:13 +0300
commit47b1030612f4382a976be6aa2369cf5d973ca154 (patch)
tree938a12f51a7ea97c4714e3b9fc36b1d6d2312e84
parente32ac2459cdac01f9b177eed526a3ffa1797039d (diff)
downloadlinux-47b1030612f4382a976be6aa2369cf5d973ca154.tar.xz
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.h4
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;