From: Eric W. Biederman ebiederm@xmission.com
commit 06af8679449d4ed282df13191fc52d5ba28ec536 upstream.
Olivier Langlois has been struggling with coredumps being incompletely written in processes using io_uring.
Olivier Langlois olivier@trillion01.com writes:
io_uring is a big user of task_work and any event that io_uring made a task waiting for that occurs during the core dump generation will generate a TIF_NOTIFY_SIGNAL.
Here are the detailed steps of the problem:
- io_uring calls vfs_poll() to install a task to a file wait queue with io_async_wake() as the wakeup function cb from io_arm_poll_handler()
- wakeup function ends up calling task_work_add() with TWA_SIGNAL
- task_work_add() sets the TIF_NOTIFY_SIGNAL bit by calling set_notify_signal()
The coredump code deliberately supports being interrupted by SIGKILL, and depends upon prepare_signal to filter out all other signals. Now that signal_pending includes wake ups for TIF_NOTIFY_SIGNAL this hack in dump_emitted by the coredump code no longer works.
Make the coredump code more robust by explicitly testing for all of the wakeup conditions the coredump code supports. This prevents new wakeup conditions from breaking the coredump code, as well as fixing the current issue.
The filesystem code that the coredump code uses already limits itself to only aborting on fatal_signal_pending. So it should not develop surprising wake-up reasons either.
v2: Don't remove the now unnecessary code in prepare_signal.
Cc: stable@vger.kernel.org Fixes: 12db8b690010 ("entry: Add support for TIF_NOTIFY_SIGNAL") Reported-by: Olivier Langlois olivier@trillion01.com Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/coredump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/coredump.c +++ b/fs/coredump.c @@ -519,7 +519,7 @@ static bool dump_interrupted(void) * but then we need to teach dump_write() to restart and clear * TIF_SIGPENDING. */ - return signal_pending(current); + return fatal_signal_pending(current) || freezing(current); }
static void wait_for_dump_helpers(struct file *file)