Re: Overriding qouta limits in Linux kernel

Jan Kara (jack@suse.cz)
Wed, 24 Oct 2001 17:35:33 +0200


Hello,

> Almost any suid binary may be used to create large files overriding quota
> limits.
Yes.

> When setuid-root binary inherits file descriptors from user process it may
> write to it without respecting the quota restrictions. This is because
> suid process has CAP_SYS_RESOURCE effective capability enabled during
> writing to the file. Quota does not know anything about who opened file
> descriptor and checks current process privileges only. This is bug in
> kernel and not in those setuid-root binaries.
Actually I think this is not a bug, it's a feature... If some process
has a CAP_SYS_RESOURCE capability then it can override the limits (that's
how I understand this capability). Hence it's got right to exceed user quota.
I think this is reasonable behaviour (root can do anything - suid binaries are
just making the will of root ;)).
And BTW I know about no way how to know who opened the file...

Honza

--
Jan Kara <jack@suse.cz>
SuSE CR Labs
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/