On Tue, 27 May 2008 00:19:32 +0200 (CEST) Jiri Kosina <jkosina@xxxxxxx> wrote:
On Mon, 26 May 2008, Geert Uytterhoeven wrote:
Recently I noticed a regression when running an old libc5 binary
(amiga-lilo) on m68k. It fails with the error message:
Hmm, libc5 is known to make broken assumptions about brk location, that's
why we introduced CONFIG_COMPAT_BRK, do you have that option turned on?
So I bisected it to:
commit 4cc6028d4040f95cdb590a87db478b42b8be0508
Author: Jiri Kosina <jkosina@xxxxxxx>
Date: Wed Feb 6 22:39:44 2008 +0100
brk: check the lower bound properly
Indeed, this should take CONFIG_COMPAT_BRK into account. Does the patch
below fix it? (assuming that you have CONFIG_COMPAT_BRK=y):
From: Jiri Kosina <jkosina@xxxxxxx>
brk: check lower bound properly
The check in sys_brk() on minimum value the brk might have must take
CONFIG_COMPAT_BRK setting into account. When this option is turned on
(i.e. we support ancient legacy binaries, e.g. libc5-linked stuff), the
lower bound on brk value is mm->end_code, otherwise the brk start is
allowed to be arbitrarily shifted.
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
diff --git a/mm/mmap.c b/mm/mmap.c
index fac6633..834118b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -245,10 +245,16 @@ asmlinkage unsigned long sys_brk(unsigned long brk)
unsigned long rlim, retval;
unsigned long newbrk, oldbrk;
struct mm_struct *mm = current->mm;
+ unsigned long min_brk;
down_write(&mm->mmap_sem);
- if (brk < mm->start_brk)
+#ifdef CONFIG_COMPAT_BRK
+ min_brk = mm->end_code;
+#else
+ min_brk = mm->start_brk;
+#endif
+ if (brk < min_brk)
goto out;
OK, we have a problem here.
Somebody has gone and checked this patch into their tree and it now
appears in linux-next.
I do not know how to work out how this patch got into linux-next.
It's not in any of the trees which I pull so I guess that person has
been shuffling URLs without telling me.
One of the reasons this is bad is that, frankly, I trust almost nobody
to remember to backport fixes into 2.6.25.x. I'm not even at all
confident that our mystery new part-time memory management maintainer
will remember to merge this into 2.6.26. The fact that this person
failed to add a Cc:stable@xxxxxxxxxx to the changelog doesn't inspire
confidence.
I shall merge this fix into my tree (y'know - the one where memory
management patches are hosted) and I'll get it into 2.6.26 and shall
offer it to the -stable team. This will cause me to get collisions
with the duplicated patch in linux-next but fortunately it is small.
This time.
And to whoever did this: please don't.
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