On 07/12/2017 04:55 AM, Ernesto A. Fernández wrote:
> When changing a file's acl mask, __jfs_set_acl() will first set the group
> bits of i_mode to the value of the mask, and only then set the actual
> extended attribute representing the new acl.
>
> If the second part fails (due to lack of space, for example) and the file
> had no acl attribute to begin with, the system will from now on assume
> that the mask permission bits are actual group permission bits, potentially
> granting access to the wrong users.
>
> Prevent this by only changing the inode mode after the acl has been set.
This looks good to me. I'll add it to the jfs queue.
Thanks,
Shaggy
>
> Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx>
> ---
> fs/jfs/acl.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
> index 7bc186f..db5a385 100644
> --- a/fs/jfs/acl.c
> +++ b/fs/jfs/acl.c
> @@ -73,16 +73,17 @@ static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
> int rc;
> int size = 0;
> char *value = NULL;
> + int update_mode = 0;
> + umode_t mode = inode->i_mode;
>
> switch (type) {
> case ACL_TYPE_ACCESS:
> ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
> if (acl) {
> - rc = posix_acl_update_mode(inode, &inode->i_mode, &acl);
> + rc = posix_acl_update_mode(inode, &mode, &acl);
> if (rc)
> return rc;
> - inode->i_ctime = current_time(inode);
> - mark_inode_dirty(inode);
> + update_mode = 1;
> }
> break;
> case ACL_TYPE_DEFAULT:
> @@ -105,8 +106,14 @@ static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
> out:
> kfree(value);
>
> - if (!rc)
> + if (!rc) {
> set_cached_acl(inode, type, acl);
> + if (update_mode) {
> + inode->i_mode = mode;
> + inode->i_ctime = current_time(inode);
> + mark_inode_dirty(inode);
> + }
> + }
>
> return rc;
> }
>
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