Re: Linux 2.2.0 is now available

[Steven Pritchard <steve@osiris.silug.org>]

Mark Bishop said:
> What was the fix?

-- Forwarded message --

Date:   Wed, 27 Jan 1999 14:11:57 +0100 (CET)
From: MOLNAR Ingo <mingo@chiara.csoma.elte.hu>
To: linux-kernel@vger.rutgers.edu, linux-smp@vger.rutgers.edu
Subject: [patch] 'coredump crash' fixed
Message-ID: <Pine.LNX.3.96.990127140714.16270A-100000@chiara.csoma.elte.hu>


it was a very subtle bug and has nothing to do with coredumps at all, but
it's very rare and the invalid coredump ELF layout accidentally triggered
the bug.

with the attached patch applied i get:

[root@moon /root]# ldd core
        not a dynamic executable
[root@moon /root]#

just as expected. The reason why we crash and why it made the kernel
reboot in such a nasty way was that munmap() did just a tad more work than
necessary and we zapped 0xc0000000's page table entry ... that is a pretty
vital piece of 4M virtual space on Linux ;) (erm, just dont ask me how i
managed to debug this ;)

-- mingo, running a hopefully much safer kernel now ;)

--- linux/mm/mmap.c.orig        Wed Jan 27 14:09:31 1999
+++ linux/mm/mmap.c     Wed Jan 27 14:06:09 1999
@@ -558,7 +558,7 @@
        unsigned long start, unsigned long end)
 {
        unsigned long first = start & PGDIR_MASK;
-       unsigned long last = (end & PGDIR_MASK) + PGDIR_SIZE;
+       unsigned long last = ((end-1) & PGDIR_MASK) + PGDIR_SIZE;
 
        if (!prev) {
                prev = mm->mmap;

-- End of forwarded message --

Some other minor stuff, like a IDE SCSI emulation bug fix, made it in,
if I'm not mistaken.

Steve
-- 
steve@silug.org           | Linux Users of Central Illinois
(217)698-1694             | Meetings the 4th Tuesday of every month
Steven Pritchard          | http://www.luci.org/ for more info

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