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. 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
