From: Jann Horn <jannh@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>,
Russell King <linux@armlinux.org.uk>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Mark Salter <msalter@redhat.com>,
Aurelien Jacquiot <jacquiot.aurelien@gmail.com>,
linux-c6x-dev@linux-c6x.org,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>,
Linux-sh list <linux-sh@vger.kernel.org>
Subject: Re: [PATCH 2/5] coredump: Fix handling of partial writes in dump_emit()
Date: Tue, 28 Apr 2020 07:52:20 +0200 [thread overview]
Message-ID: <CAG48ez0Nz8Bnty2aKdsUeMoXkjc_Bcxr+EcStZ7LBTOgRt1mrQ@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wjSYTpTH0X8EcGGJD84tsJS62BN3tC6NfzmjvXdSkFVxg@mail.gmail.com>
On Tue, Apr 28, 2020 at 5:36 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Mon, Apr 27, 2020 at 8:28 PM Jann Horn <jannh@google.com> wrote:
> >
> > After a partial write, we have to update the input buffer pointer.
>
> Interesting. It seems this partial write case never triggers (except
> for actually killing the core-dump).
>
> Or did you find a case where it actually matters?
>
> Your fix is obviously correct, but it also makes me go "that function
> clearly never actually worked for partial writes, maybe we shouldn't
> even bother?"
Hmm, yeah... I can't really think of cases where write handlers can
spuriously return early without having a pending signal, and a second
write is likely to succeed... I just know that there are some things
that are notorious for returning short *reads* (e.g. pipes, sockets,
/proc/$pid/maps).
Al's commit message refers to pipes specifically; but even at commit
2507a4fbd48a, I don't actually see where pipe_write() could return a
short write without a page allocation failure or something like that.
So maybe you're right and we should just get rid of it...
next prev parent reply other threads:[~2020-04-28 5:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 3:27 [PATCH 0/5] Fix ELF / FDPIC ELF core dumping, and use mmap_sem properly in there Jann Horn
2020-04-28 3:27 ` [PATCH 1/5] binfmt_elf_fdpic: Stop using dump_emit() on user pointers on !MMU Jann Horn
2020-04-28 3:27 ` [PATCH 2/5] coredump: Fix handling of partial writes in dump_emit() Jann Horn
2020-04-28 3:35 ` Linus Torvalds
2020-04-28 5:52 ` Jann Horn [this message]
2020-04-28 16:40 ` Rob Landley
2020-04-28 16:40 ` Linus Torvalds
2020-04-28 3:27 ` [PATCH 3/5] coredump: Refactor page range dumping into common helper Jann Horn
2020-04-28 3:27 ` [PATCH 4/5] binfmt_elf, binfmt_elf_fdpic: Use a VMA list snapshot Jann Horn
2020-04-28 3:27 ` [PATCH 5/5] mm/gup: Take mmap_sem in get_dump_page() Jann Horn
2020-04-28 3:50 ` Linus Torvalds
2020-04-28 6:10 ` Jann Horn
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