Commit b45c6e76 authored Jan 08, 2010 by Andi Kleen Committed by Linus Torvalds Jan 11, 2010

kernel/signal.c: fix kernel information leak with print-fatal-signals=1



When print-fatal-signals is enabled it's possible to dump any memory
reachable by the kernel to the log by simply jumping to that address from
user space.

Or crash the system if there's some hardware with read side effects.

The fatal signals handler will dump 16 bytes at the execution address,
which is fully controlled by ring 3.

In addition when something jumps to a unmapped address there will be up to
16 additional useless page faults, which might be potentially slow (and at
least is not very efficient)

Fortunately this option is off by default and only there on i386.

But fix it by checking for kernel addresses and also stopping when there's
a page fault.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent bd4f490a

kernel/signal.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -979,7 +979,8 @@ static void print_fatal_signal(struct pt_regs *regs, int signr)
		for (i = 0; i < 16; i++) {
		unsigned char insn;

		__get_user(insn, (unsigned char *)(regs->ip + i));
		if (get_user(insn, (unsigned char *)(regs->ip + i)))
		break;
		printk("%02x ", insn);
		}
		}

Admin message