diff options
| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-03-09 15:22:33 -0500 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-03-17 15:04:23 +0100 |
| commit | 0efbe7c4f948eb1233ef52c1cdba0b4ff973df36 (patch) | |
| tree | ee4c0c236d1e706f8bbe8d2c18a83e48b4c1414d /fs/overlayfs | |
| parent | 504f38410a51f513606c3c18c7f6a32c1ca2afb5 (diff) | |
ovl: 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")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Fixes: cbe7fba8edfc ("ovl: make sure that real fid is 32bit aligned in memory")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/overlayfs.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index ea531b1075f2..e81fea86139e 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -87,7 +87,7 @@ struct ovl_fb { u8 flags; /* OVL_FH_FLAG_* */ u8 type; /* fid_type of fid */ uuid_t uuid; /* uuid of filesystem */ - u32 fid[0]; /* file identifier should be 32bit aligned in-memory */ + u32 fid[]; /* file identifier should be 32bit aligned in-memory */ } __packed; /* In-memory and on-wire format for overlay file handle */ |