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authorEric W. Biederman <ebiederm@xmission.com>2021-06-10 15:11:11 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-10 14:02:29 -0700
commit06af8679449d4ed282df13191fc52d5ba28ec536 (patch)
tree0258a6ca24b194bfe7f7ad5a15752529f0a65852 /arch
parentf09eacca59d27efc15001795c33dbc78ca070732 (diff)
coredump: Limit what can interrupt coredumps
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: > 1. 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() > 2. wakeup function ends up calling task_work_add() with TWA_SIGNAL > 3. 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>
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