Messages in this thread Patch in this message | | | Date | Fri, 25 Mar 2011 11:20:23 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [regression v2.6.38] Re: [PATCH v2] brk: fix min_brk lower bound computation for COMPAT_BRK |
| |
On Thu, 24 Mar 2011, Geert Uytterhoeven wrote:
> > From: Jiri Kosina <jkosina@suse.cz> > > Subject: [PATCH] brk: fix min_brk lower bound computation for COMPAT_BRK > > > > Even if CONFIG_COMPAT_BRK is set in the kernel configuration, it can still > > be overriden by randomize_va_space sysctl. > > > > If this is the case, the min_brk computation in sys_brk() implementation > > is wrong, as it solely takes into account COMPAT_BRK setting, assuming > > that brk start is not randomized. But that might not be the case if > > randomize_va_space sysctl has been set to '2' at the time the binary has > > been loaded from disk. > > > > In such case, the check has to be done in a same way as in > > !CONFIG_COMPAT_BRK case. > > > > In addition to that, the check for the COMPAT_BRK case introduced back in > > a5b4592c ("brk: make sys_brk() honor COMPAT_BRK when computing lower > > bound") is slightly wrong -- the lower bound shouldn't be mm->end_code, > > but mm->end_data instead, as that's where the legacy applications expect > > brk section to start (i.e. immediately after last global variable). > > > > Signed-off-by: Jiri Kosina <jkosina@suse.cz> > > --- > > mm/mmap.c | 10 +++++++++- > > 1 files changed, 9 insertions(+), 1 deletions(-) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index 50a4aa0..ca2f164 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -253,7 +253,15 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) > > down_write(&mm->mmap_sem); > > > > #ifdef CONFIG_COMPAT_BRK > > - min_brk = mm->end_code; > > + /* > > + * CONFIG_COMPAT_BRK can still be overridden by setting > > + * randomize_va_space to 2, which will still make mm->start_brk > > + * to be arbitrarily shifted > > + */ > > + if (mm->start_brk > PAGE_ALIGN(mm->end_data)) > > + min_brk = mm->start_brk; > > + else > > + min_brk = mm->end_data; > > #else > > min_brk = mm->start_brk; > > #endif > > -- > > 1.7.3.1 > > Sorry for chiming in this late, but I've just bisected a problem in > 2.6.38 to commit > 5520e89485252c759ee60d313e9422447659947b ("brk: fix min_brk lower bound > computation for COMPAT_BRK"). > > When booting my very old test ramdisk on Amiga/m68k, it fails like this: > > | RAMDISK: gzip image found at block 0 > | VFS: Mounted root (ext2 filesystem) readonly on device 1:0. > | warning: process `update' used the obsolete bdflush system call > | Fix your initscripts? > | init: cannot open inittab > | Kernel panic - not syncing: Attempted to kill init! > > Sorry for not noticing earlier, I usually boot full Debians under ARAnyM, > instead of booting old ramdisks with libc5-based binaries that once were > considered new.
Oh well, one has to love the libc5-based binaries indeed.
Is the patch below fixing the issue you are seeing on your Amiga/m68k? Thanks.
diff --git a/mm/mmap.c b/mm/mmap.c index 2ec8eb5..0a02531 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -262,7 +262,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) if (mm->start_brk > PAGE_ALIGN(mm->end_data)) min_brk = mm->start_brk; else - min_brk = mm->end_data; + min_brk = mm->end_code; #else min_brk = mm->start_brk; #endif
-- Jiri Kosina SUSE Labs, Novell Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |