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SubjectRe: Overriding qouta limits in Linux kernel
  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
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