Re: [RFC/PATCH] revoke/frevoke system calls

From: Albert Cahalan
Date: Sat Jul 22 2006 - 04:03:34 EST

Edgar Toernig writes:
Bjvrn Steinbrink wrote:

In do_revoke() there is:

+ if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER)) {
+ ret = -EPERM;
+ goto out;

That pretty much matches what the BSD manpage says.

Urgs, so any user may remove mappings from another process and
let it crash?

Two good solutions come to mind:

a. substitute the zero page
b. make the mapping private and touch it as if C-O-W happened

Other concerns:

Optionally excluding the current UID/TGID/TID would be good.
(some flags) A revokeat() call seems to be required. Be sure
to handle working directories. The controlling tty is special.
Flag processes with revoked ttys in /proc/*/stat please, so
that ps can report it properly without opening another file.

BTW, it is wonderful to see this happening.
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