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Subject: Re: [PATCH] coredump: Limit what can interrupt coredumps
From: Olivier Langlois <olivier@trillion01.com>
To: Jens Axboe <axboe@kernel.dk>,
Tony Battersby <tonyb@cybernetics.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
io-uring <io-uring@vger.kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Pavel Begunkov>" <asml.silence@gmail.com>
Date: Sat, 21 Aug 2021 05:52:50 -0400
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On Tue, 2021-08-17 at 12:24 -0600, Jens Axboe wrote:
>
> And assuming that works, then I suspect this one would fix your issue
> even with a piped core dump:
>
> diff --git a/fs/coredump.c b/fs/coredump.c
> index 07afb5ddb1c4..852737a9ccbf 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -41,6 +41,7 @@
> #include <linux/fs.h>
> #include <linux/path.h>
> #include <linux/timekeeping.h>
> +#include <linux/io_uring.h>
>
> #include <linux/uaccess.h>
> #include <asm/mmu_context.h>
> @@ -603,6 +604,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
> };
>
> audit_core_dumps(siginfo->si_signo);
> + io_uring_task_cancel();
>
> binfmt = mm->binfmt;
> if (!binfmt || !binfmt->core_dump)
>
That is what my patch is doing. Function call is inserted at a
different place... I am not sure if one location is better than the
other or if it matters at all but there is an extra change required to
make it work...
diff --git a/fs/coredump.c b/fs/coredump.c
index 07afb5ddb1c4..614fe7a54c1a 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -41,6 +41,7 @@
#include <linux/fs.h>
#include <linux/path.h>
#include <linux/timekeeping.h>
+#include <linux/io_uring.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
@@ -625,6 +626,8 @@ void do_coredump(const kernel_siginfo_t *siginfo)
need_suid_safe = true;
}
+ io_uring_task_cancel();
+
retval = coredump_wait(siginfo->si_signo, &core_state);
if (retval < 0)
goto fail_creds;