Messages in this thread Patch in this message | | | Subject | [PATCH] Capabilities: BUG when an invalid capability is requested | From | Eric Paris <> | Date | Wed, 29 Oct 2008 11:42:12 -0400 |
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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>
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kernel/capability.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/kernel/capability.c b/kernel/capability.c index 33e51e7..50d9d99 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -498,6 +498,11 @@ 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;
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