Messages in this thread Patch in this message | | | From | Nelson Elhage <> | Subject | [PATCH v2] do_exit(): Make sure we run with get_fs() == USER_DS. | Date | Tue, 30 Nov 2010 21:27:36 -0500 |
| |
If a user manages to trigger an oops with fs set to KERNEL_DS, fs is not otherwise reset before do_exit(). do_exit may later (via mm_release in fork.c) do a put_user to a user-controlled address, potentially allowing a user to leverage an oops into a controlled write into kernel memory.
A more logical place to put this might be when we know an oops has occurred, before we call do_exit(), but that would involve changing every architecture, in multiple places. Let's just stick it in do_exit instead.
Signed-off-by: Nelson Elhage <nelhage@ksplice.com> --- kernel/exit.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c index 21aa7b3..68899b3 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -914,6 +914,14 @@ NORET_TYPE void do_exit(long code) if (unlikely(!tsk->pid)) panic("Attempted to kill the idle task!"); + /* + * If do_exit is called because this processes oopsed, it's possible + * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before + * continuing. This is relevant at least for clearing clear_child_tid in + * mm_release. + */ + set_fs(USER_DS); + tracehook_report_exit(&code); validate_creds_for_do_exit(tsk); -- 1.7.1.31.g6297e
| |