[LWN Logo]

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


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;


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/