Red Hat Bugzilla – Bug 3568
RHSA: NFS root squashing broken with 32 bit uid_t
Last modified: 2015-01-07 18:37:43 EST
It's that time of the year again...
Someone just mailed me about a problem he was having with
in passing he mentioned that Linux refuses setfsuid(-2).
Unfortunately, unfsd relies on this for root squashing
defined a different anon uid/gid).
The cause of the problem is glibc's move to 32 bit uid_t,
while the kernel remains at 16 bit. To compensate for this,
glibc setfsuid() implementation has some hideously `clever'
setfsuid (uid_t uid)
if (uid != (uid_t) ((__kernel_uid_t) uid))
return INLINE_SYSCALL (setfsuid, 1, uid);
It is entirely possible that other applications are affected
symptoms as well, because seteuid exhibits the same
A patched unfsd (2.2.beta44) will be available shortly from
Jay, this 5.2 errata package needs QA: