From: Oscar Salvador <osalvador@techadventures.net>
To: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
syzbot <syzbot+5dcb560fe12aa5091c06@syzkaller.appspotmail.com>,
akpm@linux-foundation.org, aneesh.kumar@linux.vnet.ibm.com,
dan.j.williams@intel.com, kirill.shutemov@linux.intel.com,
linux-mm@kvack.org, mst@redhat.com,
syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk,
ying.huang@intel.com
Subject: Re: kernel BUG at mm/gup.c:LINE!
Date: Thu, 5 Jul 2018 14:30:17 +0200 [thread overview]
Message-ID: <20180705123017.GA31959@techadventures.net> (raw)
In-Reply-To: <20180705071839.GB30187@techadventures.net>
On Thu, Jul 05, 2018 at 09:18:39AM +0200, Oscar Salvador wrote:
>
> > This is more than unexpected. The patch merely move the alignment check
> > up. I will try to investigate some more but I am off for next four days
> > and won't be online most of the time.
> >
> > Btw. does the same happen if you keep do_brk helper and add the length
> > sanitization there as well?
I took another look.
The problem was that while deleting the check in do_brk_flags(), this left then "len"
local variable with an unset value, but we need it to contain the request value
because we do use it in further calls in do_brk_flags(), like:
while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
&rb_parent)) {
if (do_munmap(mm, addr, len, uf))
return -ENOMEM;
}
or
if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
and so on.
This boots and works with the reproducer:
diff --git a/mm/mmap.c b/mm/mmap.c
index 9859cd4e19b9..e4c9e995870f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -186,8 +186,8 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
return next;
}
-static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf);
-
+static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
+ struct list_head *uf);
SYSCALL_DEFINE1(brk, unsigned long, brk)
{
unsigned long retval;
@@ -245,7 +245,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
goto out;
/* Ok, looks good - let it rip. */
- if (do_brk(oldbrk, newbrk-oldbrk, &uf) < 0)
+ if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
goto out;
set_brk:
@@ -2934,17 +2934,11 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
- unsigned long len;
+ unsigned long len = request;
struct rb_node **rb_link, *rb_parent;
pgoff_t pgoff = addr >> PAGE_SHIFT;
int error;
- len = PAGE_ALIGN(request);
- if (len < request)
- return -ENOMEM;
- if (!len)
- return 0;
-
/* Until we need other flags, refuse anything except VM_EXEC. */
if ((flags & (~VM_EXEC)) != 0)
return -EINVAL;
@@ -3016,18 +3010,20 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long
return 0;
}
-static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf)
-{
- return do_brk_flags(addr, len, 0, uf);
-}
-
-int vm_brk_flags(unsigned long addr, unsigned long len, unsigned long flags)
+int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
{
struct mm_struct *mm = current->mm;
int ret;
+ unsigned long len;
bool populate;
LIST_HEAD(uf);
+ len = PAGE_ALIGN(request);
+ if (len < request)
+ return -ENOMEM;
+ if (!len)
+ return 0;
+
if (down_write_killable(&mm->mmap_sem))
return -EINTR;
But I think that we should also add:
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 0ac456b52bdd..6c7e005ae12d 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1259,9 +1259,9 @@ static int load_elf_library(struct file *file)
goto out_free_ph;
}
- len = ELF_PAGESTART(eppnt->p_filesz + eppnt->p_vaddr +
- ELF_MIN_ALIGN - 1);
- bss = eppnt->p_memsz + eppnt->p_vaddr;
+
+ len = ELF_PAGEALIGN(eppnt->p_filesz + eppnt->p_vaddr);
+ bss = ELF_PAGEALIGN(eppnt->p_memsz + eppnt->p_vaddr);
if (bss > len) {
error = vm_brk(len, bss - len);
if (error)
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2018-07-05 12:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-04 4:19 kernel BUG at mm/gup.c:LINE! syzbot
2018-07-04 10:01 ` Tetsuo Handa
2018-07-04 11:17 ` Michal Hocko
2018-07-04 11:48 ` Zi Yan
2018-07-04 12:11 ` Michal Hocko
2018-07-04 15:15 ` Oscar Salvador
2018-07-05 0:35 ` Tetsuo Handa
2018-07-05 7:18 ` Oscar Salvador
2018-07-05 11:40 ` Oscar Salvador
2018-07-05 6:44 ` Michal Hocko
2018-07-05 7:18 ` Oscar Salvador
2018-07-05 12:30 ` Oscar Salvador [this message]
2018-07-05 13:40 ` Tetsuo Handa
2018-07-06 5:35 ` Michal Hocko
2018-07-06 7:40 ` Oscar Salvador
2018-07-06 7:50 ` [PATCH] mm: do not bug_on on incorrect lenght in __mm_populate kbuild test robot
2018-07-06 8:23 ` Oscar Salvador
2018-07-06 9:02 ` Michal Hocko
2018-07-04 12:12 ` kernel BUG at mm/gup.c:LINE! Oscar Salvador
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180705123017.GA31959@techadventures.net \
--to=osalvador@techadventures.net \
--cc=akpm@linux-foundation.org \
--cc=aneesh.kumar@linux.vnet.ibm.com \
--cc=dan.j.williams@intel.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mst@redhat.com \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=syzbot+5dcb560fe12aa5091c06@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=viro@zeniv.linux.org.uk \
--cc=ying.huang@intel.com \
--cc=zi.yan@cs.rutgers.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).