From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx124.postini.com [74.125.245.124]) by kanga.kvack.org (Postfix) with SMTP id 324256B0006 for ; Mon, 11 Mar 2013 19:03:24 -0400 (EDT) Date: Mon, 11 Mar 2013 16:03:22 -0700 From: Andrew Morton Subject: Re: [PATCH 4/9] mm: use mm_populate() for blocking remap_file_pages() Message-Id: <20130311160322.830cc6b670fd24faa8366413@linux-foundation.org> In-Reply-To: References: <1356050997-2688-1-git-send-email-walken@google.com> <1356050997-2688-5-git-send-email-walken@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tommi Rantala Cc: Michel Lespinasse , Andy Lutomirski , Ingo Molnar , Al Viro , Hugh Dickins , Jorn_Engel , Rik van Riel , "linux-mm@kvack.org" , LKML , Dave Jones On Sun, 10 Mar 2013 20:55:21 +0200 Tommi Rantala wrote: > 2012/12/21 Michel Lespinasse : > > Signed-off-by: Michel Lespinasse > > Hello, this patch introduced the following bug, seen while fuzzing with trinity: > > [ 396.825414] BUG: unable to handle kernel NULL pointer dereference > at 0000000000000050 > > ... > > > + vm_flags = vma->vm_flags; > > When find_vma() fails, vma is NULL here. Yup, thanks. This, methinks: From: Andrew Morton Subject: mm/fremap.c: fix oops on error path If find_vma() fails, sys_remap_file_pages() will dereference `vma', which contains NULL. Fix it by checking the pointer. (We could alternatively check for err==0, but this seems more direct) (The vm_flags change is to squish a bogus used-uninitialised warning without adding extra code). Reported-by: Tommi Rantala Cc: Michel Lespinasse Signed-off-by: Andrew Morton --- mm/fremap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff -puN mm/fremap.c~mm-fremapc-fix-oops-on-error-path mm/fremap.c --- a/mm/fremap.c~mm-fremapc-fix-oops-on-error-path +++ a/mm/fremap.c @@ -163,7 +163,8 @@ SYSCALL_DEFINE5(remap_file_pages, unsign * and that the remapped range is valid and fully within * the single existing vma. */ - if (!vma || !(vma->vm_flags & VM_SHARED)) + vm_flags = vma->vm_flags; + if (!vma || !(vm_flags & VM_SHARED)) goto out; if (!vma->vm_ops || !vma->vm_ops->remap_pages) @@ -254,7 +255,8 @@ get_write_lock: */ out: - vm_flags = vma->vm_flags; + if (vma) + vm_flags = vma->vm_flags; if (likely(!has_write_lock)) up_read(&mm->mmap_sem); else _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org