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Re: [PATCH v2] Fix read after xfree in linux_nat_detach
OK.
On 03/23/2017 01:17 PM, Philipp Rudo wrote:
> On Wed, 22 Mar 2017 17:26:27 +0000
> Pedro Alves <palves@redhat.com> wrote:
>
>> On 03/22/2017 05:16 PM, Philipp Rudo wrote:
>>
>>> Looks like we can get simply rid of it. I'll see that I get a test
>>> case running which forks to verify it, tomorrow.
>>
>> This forks handling is the support for the "checkpoint" &
>> friends commands, covered by gdb.base/checkpoint.exp.
>> Doesn't seem to exercise detach yet though, unfortunately.
>
> I double checked, the same bug also happens when checkpointing. The
> fix now is simply to remove delete_lwp at the end of linux_nat_detach.
>
> Although testing detach would be good, I'm not sure if the testsuite
> would have found this bug.
>
> ---
>
> From ee3dced0b22cc1edb10a82aeb79ae35d78d665bc Mon Sep 17 00:00:00 2001
> From: Philipp Rudo <prudo@linux.vnet.ibm.com>
> Date: Wed, 22 Mar 2017 13:53:50 +0100
> Subject: [PATCH v2] Fix read after xfree in linux_nat_detach
>
> At the end of linux_nat_detach the main_lwp is deleted (delete_lwp).
> This is problematic as during detach (detach_one_lwp and
> linux_fork_detach) main_lwp already gets freed. Thus calling
> delete_lwp causes a read after free. Fix it by removing the
> unnecessary delete_lwp.
>
> gdb/ChangeLog:
> * linux-nat.c (linux_nat_detach): delete_lwp causes read after
> free. Remove it.
> ---
> gdb/linux-nat.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> index dff0da5..efe7daf 100644
> --- a/gdb/linux-nat.c
> +++ b/gdb/linux-nat.c
> @@ -1549,7 +1549,6 @@ linux_nat_detach (struct target_ops *ops, const
> char *args, int from_tty)
> inf_ptrace_detach_success (ops);
> }
> - delete_lwp (main_lwp->ptid);
> }
>
> /* Resume execution of the inferior process. If STEP is nonzero,
>
--
Thanks,
Pedro Alves