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| author |   Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 13:39:09 -0500 |
|---|---|---|
| committer |   Johannes Berg <johannes.berg@intel.com> | 2020-05-27 10:02:03 +0200 |
| commit | 396fba0a59f3c94d6fd6443fbeabd8bd9e3956eb (patch) | |
| tree | 8c67834035dab2e879e89f27bdc5927af865ef02 /include/net | |
| parent | mac80211: Add new AMPDU factor macro for HE peer caps (diff) | |
| download | wireguard-linux-396fba0a59f3c94d6fd6443fbeabd8bd9e3956eb.tar.xz wireguard-linux-396fba0a59f3c94d6fd6443fbeabd8bd9e3956eb.zip | |
cfg80211: 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>
Link: https://lore.kernel.org/r/20200507183909.GA12993@embeddedor
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Diffstat (limited to 'include/net')
| -rw-r--r-- | include/net/cfg80211.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h index 7415f77d99ca..021366cfb2b0 100644 --- a/include/net/cfg80211.h +++ b/include/net/cfg80211.h @@ -2037,7 +2037,7 @@ struct cfg80211_scan_request { bool no_cck; /* keep last */ - struct ieee80211_channel *channels[0]; + struct ieee80211_channel *channels[]; }; static inline void get_random_mask_addr(u8 *buf, const u8 *addr, const u8 *mask) @@ -2183,7 +2183,7 @@ struct cfg80211_sched_scan_request { struct list_head list; /* keep last */ - struct ieee80211_channel *channels[0]; + struct ieee80211_channel *channels[]; }; /** @@ -2305,7 +2305,7 @@ struct cfg80211_bss { u8 bssid_index; u8 max_bssid_indicator; - u8 priv[0] __aligned(sizeof(void *)); + u8 priv[] __aligned(sizeof(void *)); }; /** @@ -4852,7 +4852,7 @@ struct wiphy { u8 max_data_retry_count; - char priv[0] __aligned(NETDEV_ALIGN); + char priv[] __aligned(NETDEV_ALIGN); }; static inline struct net *wiphy_net(struct wiphy *wiphy) |