From c2d0699c629d30dde3329003baac3b94f1d717e6 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 9 Mar 2020 13:04:41 -0500 Subject: [PATCH] ext2: xattr.h: 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") Link: https://lore.kernel.org/r/20200309180441.GA2992@embeddedor Signed-off-by: Gustavo A. R. Silva Signed-off-by: Jan Kara --- fs/ext2/xattr.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext2/xattr.h b/fs/ext2/xattr.h index cee888c..16272e6 100644 --- a/fs/ext2/xattr.h +++ b/fs/ext2/xattr.h @@ -39,7 +39,7 @@ struct ext2_xattr_entry { __le32 e_value_block; /* disk block attribute is stored on (n/i) */ __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 EXT2_XATTR_PAD_BITS 2 -- 2.7.4