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Make preparations for resurrecting shared/read locks on vm maps:

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mac_proc_vm_revoke_recurse() requests a read lock on the vm map at the start
but does not handle failure by vm_map_lock_upgrade() when it seeks to modify
the vm map.  At present, this works because all lock request on a vm map are
implemented as exclusive locks.  Thus, vm_map_lock_upgrade() is a no-op that
always reports success.  However, that is about to change, and
proc_vm_revoke_recurse() will require substantial modifications to handle
vm_map_lock_upgrade() failures.  For the time being, I am changing
mac_proc_vm_revoke_recurse() to request a write lock on the vm map at the
start.

Approved by:	rwatson
MFC after:	3 months
This commit is contained in:
Alan Cox 2008-12-22 17:32:52 +00:00
parent d13994cec0
commit 1361cdc644
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=186397
1 changed files with 2 additions and 4 deletions
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6
sys/security/mac/mac_process.c
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@ -260,7 +260,7 @@ mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
if (!mac_mmap_revocation)
return;
vm_map_lock_read(map);
vm_map_lock(map);
for (vme = map->header.next; vme != &map->header; vme = vme->next) {
if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
mac_proc_vm_revoke_recurse(td, cred,
@ -315,7 +315,6 @@ mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
prot2str(revokeperms), (u_long)vme->start,
(long)(vme->end - vme->start),
prot2str(vme->max_protection), prot2str(vme->protection));
vm_map_lock_upgrade(map);
/*
* This is the really simple case: if a map has more
* max_protection than is allowed, but it's not being
@ -369,10 +368,9 @@ mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
vme->protection & ~revokeperms);
vm_map_simplify_entry(map, vme);
}
vm_map_lock_downgrade(map);
VFS_UNLOCK_GIANT(vfslocked);
}
vm_map_unlock_read(map);
vm_map_unlock(map);
}
int