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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 13:43:56 -0500
committerJohn Johansen <john.johansen@canonical.com>2020-05-15 13:04:55 -0700
commitfe9fd23e3b587c7ca9520717b213f88050c1d324 (patch)
tree19a983a7b1be3c2211c89741f719071d9cbc98df /security/apparmor/apparmorfs.c
parentc27c6bd2c4d6b6bb779f9b722d5607993e1d5e5c (diff)
downloadlinux-fe9fd23e3b587c7ca9520717b213f88050c1d324.tar.gz
apparmor: Replace zero-length array with flexible-array
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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 <gustavoars@kernel.org> Signed-off-by: John Johansen <john.johansen@canonical.com>
Diffstat (limited to 'security/apparmor/apparmorfs.c')
-rw-r--r--security/apparmor/apparmorfs.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index d7a179cdaa1e..d65324415980 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -807,7 +807,7 @@ static ssize_t query_label(char *buf, size_t buf_len,
struct multi_transaction {
struct kref count;
ssize_t size;
- char data[0];
+ char data[];
};
#define MULTI_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct multi_transaction))