On Fri, 14 Jun 2019 at 15:46, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > kcephfs has several "virtual" xattrs that return strings that are > currently populated using snprintf(), which always NULL terminates the > string. > > This leads to the string being truncated when we use a buffer length > acquired by calling getxattr with a 0 size first. The last character > of the string ends up being clobbered by the termination. > > The convention with xattrs is to not store the termination with string > data, given that we have the length. This is how setfattr/getfattr > operate. > > This patch makes ceph's virtual xattrs not include NULL termination > when formatting their values. In order to handle this, a new > snprintf_noterm function is added, and ceph is changed over to use > this to populate the xattr value buffer. Finally, we fix ceph to > return -ERANGE properly when the string didn't fit in the buffer. This looks reasonable from an xattr point of view. Thanks, Andreas > Jeff Layton (3): > lib/vsprintf: add snprintf_noterm > ceph: don't NULL terminate virtual xattr strings > ceph: return -ERANGE if virtual xattr value didn't fit in buffer > > fs/ceph/xattr.c | 49 +++++++------- > include/linux/kernel.h | 2 + > lib/vsprintf.c | 145 ++++++++++++++++++++++++++++------------- > 3 files changed, 130 insertions(+), 66 deletions(-) > > -- > 2.21.0 >
