On Wed 12-07-17 06:54:19, Ernesto A. Fernández wrote:
> When changing a file's acl mask, ext2_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.
>
> Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx>
Thanks for the patch! I have rebased it on top of the fix in that area that
is sitting in my tree and merged it to my tree.
Honza
> ---
> A line in acl.c is too long, and checkpatch.pl complains about it when run
> against this patch. In case it matters, the next patch will fix that.
>
> fs/ext2/acl.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
> index 79dafa7..4e04b7e 100644
> --- a/fs/ext2/acl.c
> +++ b/fs/ext2/acl.c
> @@ -185,16 +185,17 @@ ext2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
> void *value = NULL;
> size_t size = 0;
> int error;
> + int update_mode = 0;
> + umode_t mode = inode->i_mode;
>
> switch(type) {
> case ACL_TYPE_ACCESS:
> name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
> if (acl) {
> - error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
> + error = posix_acl_update_mode(inode, &mode, &acl);
> if (error)
> return error;
> - inode->i_ctime = current_time(inode);
> - mark_inode_dirty(inode);
> + update_mode = 1;
> }
> break;
>
> @@ -216,8 +217,14 @@ ext2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
> error = ext2_xattr_set(inode, name_index, "", value, size, 0);
>
> kfree(value);
> - if (!error)
> + if (!error) {
> set_cached_acl(inode, type, acl);
> + if (update_mode) {
> + inode->i_mode = mode;
> + inode->i_ctime = current_time(inode);
> + mark_inode_dirty(inode);
> + }
> + }
> return error;
> }
>
> --
> 2.1.4
>
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
