24 Mar, 2020

1 commit

  • 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
    Reviewed-by: David Sterba
    Signed-off-by: David Sterba

    Gustavo A. R. Silva
     

12 Apr, 2018

1 commit


15 Jun, 2012

1 commit

  • Al pointed out that we can just toss out the old name on a device and add a
    new one arbitrarily, so anybody who uses device->name in printk could
    possibly use free'd memory. Instead of adding locking around all of this he
    suggested doing it with RCU, so I've introduced a struct rcu_string that
    does just that and have gone through and protected all accesses to
    device->name that aren't under the uuid_mutex with rcu_read_lock(). This
    protects us and I will use it for dealing with removing the device that we
    used to mount the file system in a later patch. Thanks,

    Reviewed-by: David Sterba
    Signed-off-by: Josef Bacik

    Josef Bacik