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Message-Id: <20090907093856.5c453d3f.kamezawa.hiroyu@jp.fujitsu.com> Date: Mon, 7 Sep 2009 09:38:56 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Nick Craig-Wood <nick@...ig-wood.com>, Pekka Enberg <penberg@...helsinki.fi>, linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: Reading /proc/kcore causes a BUG() On Fri, 4 Sep 2009 10:31:56 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote: > On Fri, 4 Sep 2009 18:16:45 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote: > > > On Fri, 4 Sep 2009 10:00:39 +0100 > > Nick Craig-Wood <nick@...ig-wood.com> wrote: > > > > > On Fri, Sep 04, 2009 at 09:06:42AM +0900, KAMEZAWA Hiroyuki wrote: > > > > On Thu, 3 Sep 2009 15:14:55 +0300 > > > > Pekka Enberg <penberg@...helsinki.fi> wrote: > > > > > On Thu, Sep 3, 2009 at 2:34 PM, Nick Craig-Wood<nick@...ig-wood.com> wrote: > > > > > > Is a fix for this going to make 2.6.31? > > > > > > > > > > > > To replicate > > > > > > > > > > > > __cat /proc/kcore >/dev/null > > > > > > > > > > > > See also > > > > > > > > > > > > __http://bugzilla.kernel.org/show_bug.cgi?id=13850 > > > [snip] > > > > > > I tried this on the latest git checkout (as of 2009-09-03 11:00 GMT) > > > > > > under Xen as a domU. __The bugzilla report states it happens on non xen > > > > > > machines also. > > Is this a regression? I've lost track.. > regression. (this comes from new per-cpu area implemantation, which uses vmalloc area with memory holes.) > > > > > > I know reading /proc/kcore isn't such a good idea, but badly written > > > > > > backup scripts are triggering this on our customer's servers :-( > > > > > > > > > > AFAICT the bug was fixed but I can't seem to find the patches in > > > > > Linus' git either. Lets CC Andrew and Hiroyuki-san. > > > > > > > > Ah, it's now tested under mmotm. please wait. > > > > > > I tried mmotm but I couldn't get it to boot under Xen :-( > > > > > > If you send me a patch against latest git I'm willing to test it (I > > > tried to extract the relevant patch from mmotm but failed dismally) > > > > > > Thanks > > > > > > > If you already downloaded mmotm, use these patches. > > > > vmalloc-unmap-vmalloc-area-after-hiding-it.patch > > kcore-fix-vread-vwrite-to-be-aware-of-holes.patch > > kcore-fix-vread-vwrite-to-be-aware-of-holes-update.patch > > kcore-proc-kcore-should-use-vread.patch > > > > All I tested was x86-32/x86-64. then more tests are welcomed. > > That's a lot of stuff for 2.6.31. Is there some simple quickfix we can do? > I don't like this patch. But here, my 1st version which wasn't sent out. -Kame == /proc/kcore may access in memory holes in vmalloc area. skip it by using copy_from_user(). Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> --- fs/proc/kcore.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) Index: linux-2.6.31-rc8/fs/proc/kcore.c =================================================================== --- linux-2.6.31-rc8.orig/fs/proc/kcore.c +++ linux-2.6.31-rc8/fs/proc/kcore.c @@ -361,7 +361,9 @@ read_kcore(struct file *file, char __use /* don't dump ioremap'd stuff! (TA) */ if (m->flags & VM_IOREMAP) continue; - memcpy(elf_buf + (vmstart - start), + /* we may access memory holes */ + __copy_from_user_inatomic( + elf_buf + (vmstart - start), (char *)vmstart, vmsize); } read_unlock(&vmlist_lock); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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