On May 4, 2014, at 7:03 AM, Christoph Hellwig <hch@xxxxxx> wrote:
> Various filesystems don't bother checking for a NULL ACL in
> posix_acl_equiv_mode, and thus can dereference a NULL pointer when it
> gets passed one. This usually happens from the NFS server, as the ACL tools
> never pass a NULL ACL, but instead of one representing the mode bits.
>
> Instead of adding boilerplat to all filesystems put this check into one place,
> which will allow us to remove the check from other filesystems as well later
> on.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reported-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>
> Reported-by: Marco Munderloh <munderl@xxxxxxxxxxxxxxxxxxx>,
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
Good clean-up.
Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> fs/posix_acl.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 9e363e4..0855f77 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -246,6 +246,12 @@ posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
> umode_t mode = 0;
> int not_equiv = 0;
>
> + /*
> + * A null ACL can always be presented as mode bits.
> + */
> + if (!acl)
> + return 0;
> +
> FOREACH_ACL_ENTRY(pa, acl, pe) {
> switch (pa->e_tag) {
> case ACL_USER_OBJ:
> --
> 1.7.10.4
>
> --
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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