Messages in this thread Patch in this message | | | Date | Fri, 25 Dec 2009 21:29:56 +0100 | From | Andi Kleen <> | Subject | [PATCH] Fix kernel information leak with print-fatal-signals=1 |
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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.
Stable candidate.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
--- kernel/signal.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
Index: linux-2.6.33-rc1-ak/kernel/signal.c =================================================================== --- linux-2.6.33-rc1-ak.orig/kernel/signal.c +++ linux-2.6.33-rc1-ak/kernel/signal.c @@ -979,7 +979,8 @@ static void print_fatal_signal(struct pt 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); } }
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