On Wed 12-07-17 06:53:51, Ernesto A. Fernández wrote: > When changing a file's acl mask, __ext4_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> This clashes with my fix of another bug in that area [1] but the fixup should be straightforward. The patch looks good to me so feel free to add Reviewed-by: Jan Kara <jack@xxxxxxx> [1] https://www.spinics.net/lists/stable/msg178111.html Honza > --- > fs/ext4/acl.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c > index 09441ae..2985cd0 100644 > --- a/fs/ext4/acl.c > +++ b/fs/ext4/acl.c > @@ -189,16 +189,17 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, 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 = EXT4_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); > - ext4_mark_inode_dirty(handle, inode); > + update_mode = 1; > } > break; > > @@ -221,8 +222,14 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, int type, > value, size, xattr_flags); > > 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); > + ext4_mark_inode_dirty(handle, inode); > + } > + } > > return error; > } > -- > 2.1.4 > > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
