From: Andrew Morton
Date: Mon May 10 2004 - 17:04:47 EST
Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> > +hugetlb_shm_group-sysctl-patch.patch
> > Add /proc/sys/vm/hugetlb_shm_group: this holds the group ID of users who may
> > allocate hugetlb shm segments without CAP_IPC_LOCK. For Oracle.
> > +mlock_group-sysctl.patch
> > /proc/sys/vm/mlock_group: group ID of users who can do mlock() without
> > CAP_IPC_LOCK. Not sure that we need this.
> These two just introduced a subtile behaviour change during stable series,
> possibly (not likely) leading to DoS opportunities from applications running
> as gid 0.
mlock_group is likely to go away.
Is an unprivileged user likely to have gid 0? Easy enough to fix, anyway.
--- 25/fs/hugetlbfs/inode.c~hugetlb_shm_group-sysctl-gid-0-fix Mon May 10 14:57:31 2004
+++ 25-akpm/fs/hugetlbfs/inode.c Mon May 10 14:58:59 2004
@@ -722,8 +722,11 @@ static unsigned long hugetlbfs_counter(v
static int can_do_hugetlb_shm(void)
- return likely(capable(CAP_IPC_LOCK) ||
+ if (capable(CAP_IPC_LOCK))
+ return 1;
+ if (sysctl_hugetlb_shm_group == 0)
+ return 0;
+ return in_group_p(sysctl_hugetlb_shm_group);
struct file *hugetlb_zero_setup(size_t size)
> Really, with capabilities first and now selinux we have moved
> away from treating uid 0 special, so introducing special casing of a gid
> now is more than just braindead.
Capabilities are broken and don't work. Nobody has a clue how to provide
the required services with SELinux and nobody has any code and we need the
feature *now* before vendors go shipping even more ghastly stuff.
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