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Capabilities: BUG when an invalid capability is requested

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If an invalid (large) capability is requested the capabilities system
may panic as it is dereferencing an array of fixed (short) length.  Its
possible (and actually often happens) that the capability system
accidentally stumbled into a valid memory region but it also regularly
happens that it hits invalid memory and BUGs.  If such an operation does
get past cap_capable then the selinux system is sure to have problems as
it already does a (simple) validity check and BUG.  This is known to
happen by the broken and buggy firegl driver.

This patch cleanly checks all capable calls and BUG if a call is for an
invalid capability.  This will likely break the firegl driver for some
situations, but it is the right thing to do.  Garbage into a security
system gets you killed/bugged

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Eric Paris 2008-10-29 15:42:12 +11:00 committed by James Morris
parent e68b75a027
commit 637d32dc72
1 changed files with 5 additions and 0 deletions
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5
kernel/capability.c
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@ -514,6 +514,11 @@ asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
*/
int capable(int cap)
{
if (unlikely(!cap_valid(cap))) {
printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
BUG();
}
if (has_capability(current, cap)) {
current->flags |= PF_SUPERPRIV;
return 1;