[lkml]   [2002]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: problems with changing UID/GID
On Mon, Aug 26, 2002 at 02:45:51PM +0100, Alan Cox wrote:
> On Mon, 2002-08-26 at 14:30, Zheng Jian-Ming wrote:
> > But, the credentials are per-task in Linux, so it's possible to have
> > two tasks in a process running under different UIDs.
> Really useful isnt it
> There are other reasons for wanting refcounted credential structures (eg
> NFS writeback) so it may well be that once those go in for other reasons
> it makes sense to provide an option to do shared credentials for
> threaded apps. It is however nontrivial and you might want to see how
> your other systems respond to things like a file open on a slow device
> while a second thread is strobing the uid between two values. Does it
> change uid mid syscall, does it get the permissions checks right if so ?
> Its non trivial stuff, if not plain crazy to implement a literal
> interpretation of (eg does a write fail half way if you change userid in
> another thread ?)

Does POSIX really require that granularity of change? Would an
implementation which, say, stored all credentials per-thread/task
and only picked up changes from other threads at kernel entry/exit
not be in spec? That seems like a lower overhead solution than
locking all access to UIDs.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:28    [W:0.101 / U:7.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site