Messages in this thread | | | Date | Tue, 29 Jul 2014 09:55:10 +0800 | From | Wang Nan <> | Subject | Re: [PATCH] kprobes/x86: opt: free optinsn cache when range check fails |
| |
On 2014/7/29 9:43, Masami Hiramatsu wrote: > (2014/07/28 21:20), Wang Nan wrote: >> This patch frees optinsn slot when range check error to prevent memory >> leaks. Before this patch, cache entry in kprobe_insn_cache won't be >> freed if kprobe optimizing fails due to range check failure. >> >> Signed-off-by: Wang Nan <wangnan0@huawei.com> > > Oops, thank you for finding it! > > Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> > > BTW, would you really have hit this error? > I'd like to know the case if this really happens.
I'm not really hit it on x86_64. I found this problem when trying to implement kprobe opt on arm.
On arm, relative jump can only branch on/backward 64MB, which makes it a realistic problem.
> >> --- >> arch/x86/kernel/kprobes/opt.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c >> index f304773..f1314d0 100644 >> --- a/arch/x86/kernel/kprobes/opt.c >> +++ b/arch/x86/kernel/kprobes/opt.c >> @@ -338,8 +338,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op) >> * a relative jump. >> */ >> rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE; >> - if (abs(rel) > 0x7fffffff) >> + if (abs(rel) > 0x7fffffff) { >> + __arch_remove_optimized_kprobe(op, 0); >> return -ERANGE; >> + } >> >> buf = (u8 *)op->optinsn.insn; >> >> > >
| |