linux-kernel - Re: [PATCH] coredump: Limit what can interrupt coredumps

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Message-ID: <57f28a37c6bffacdadd4d98a7c6abc258dd752d4.camel@trillion01.com>
Date:   Sat, 21 Aug 2021 05:52:50 -0400
From:   Olivier Langlois <olivier@...llion01.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Tony Battersby <tonyb@...ernetics.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        io-uring <io-uring@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Pavel Begunkov>" <asml.silence@...il.com>
Subject: Re: [PATCH] coredump: Limit what can interrupt coredumps

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;