Re: Linux 2.4.33-rc1

Willy Tarreau
2006-06-18T22:37:50Z

Hi Grant,

On Mon, Jun 19, 2006 at 08:25:06AM +1000, Grant Coady wrote:
> On Sun, 18 Jun 2006 10:37:18 -0300, Marcelo Tosatti <marcelo@kvack.org> wrote:
>
> >Can you please try the attached patch.
> >
> >Grab a reference to the victim inode before calling vfs_unlink() to avoid
> >it vanishing under us.
> >
> >diff --git a/fs/namei.c b/fs/namei.c
> >index 42cce98..7993283 100644
> >--- a/fs/namei.c
> >+++ b/fs/namei.c
> >@@ -1509,6 +1509,7 @@ asmlinkage long sys_unlink(const char *
> > char * name;
> > struct dentry *dentry;
> > struct nameidata nd;
> >+ struct inode *inode = NULL;
> >
> > name = getname(pathname);
> > if(IS_ERR(name))
> >@@ -1527,11 +1528,16 @@ asmlinkage long sys_unlink(const char *
> > /* Why not before? Because we want correct error value */
> > if (nd.last.name[nd.last.len])
> > goto slashes;
> >+ inode = dentry->d_inode;
> >+ if (inode)
> >+ atomic_inc(&inode->i_count);
> > error = vfs_unlink(nd.dentry->d_inode, dentry);
> > exit2:
> > dput(dentry);
> > }

Could you add this line here, because your oops still looks like the NULL
is close to this area :

+ printk(KERN_DEBUG "nd.dentry->d_inode = %p\n", nd.dentry->d_inode);

> > up(&nd.dentry->d_inode->i_sem);
> >+ if (inode)
> >+ iput(inode);
> > exit1:
> > path_release(&nd);
> > exit:
>
> /home/share is an NFS mounted directory, via ssh terminal:
>
> grant@sempro:~$ dmesg >/home/share/dmesg-2.4.33-rc1a
> grant@sempro:~$ rm /home/share/dmesg-2.4.33-rc1a
> Segmentation fault
>
> Network connection lost, copy / paste oops from screen to file, reboot,
> and...
>
> ksymoops 2.4.11 on i686 2.4.33-rc1a. Options used
> -v /home/grant/linux/linux-2.4.33-rc1a/vmlinux (specified)
> -k /proc/ksyms (default)
> -l /proc/modules (default)
> -o /lib/modules/2.4.33-rc1a/ (default)
> -m /boot/System.map-2.4.33-rc1a (specified)
>
> Unable to handle kernel NULL pointer dereference at virtual address 00000088
> *pde = 00000000
> Oops: 0002
> CPU: 0
> EIP: 0010:[<c013eeb4>] Not tainted
> Using defaults from ksymoops -t elf32-i386 -a i386
> EFLAGS: 00010282
> eax: 00000000 ebx: 00000000 ecx: 00000088 edx: 00000088
> esi: f6e2ed08 edi: f5954e40 ebp: f6e2ec80 esp: f587ff68
> ds: 0018 es: 0018 ss: 0018
> Process rm (pid: 241, stackpage=f587f000)
> Stack: f6e2ec80 f5954e40 f5954e40 f75a7000 f58ca0c0 f587ff90 c013f078 f6e2ec80
> f5954e40 f5954e40 f6eb8440 c19ac440 f75a700c 00000011 c1bbcfcb 00000010
> 00000000 00000004 f587e000 bffff986 08051050 bffff768 c0106eff bffff986
> Call Trace: [<c013f078>] [<c0106eff>]
> Code: ff 80 88 00 00 00 0f 8e 58 16 00 00 85 db 74 16 89 d8 8b 5c
>
>
> >>EIP; c013eeb4 <vfs_unlink+a4/1a0> <=====
>
> >>esi; f6e2ed08 <_end+36a9305c/386be3d4>
> >>edi; f5954e40 <_end+355b9194/386be3d4>
> >>ebp; f6e2ec80 <_end+36a92fd4/386be3d4>
> >>esp; f587ff68 <_end+354e42bc/386be3d4>
>
> Trace; c013f078 <sys_unlink+c8/140>
> Trace; c0106eff <system_call+33/38>
>
> Code; c013eeb4 <vfs_unlink+a4/1a0>
> 00000000 <_EIP>:
> Code; c013eeb4 <vfs_unlink+a4/1a0> <=====
> 0: ff 80 88 00 00 00 incl 0x88(%eax) <=====
> Code; c013eeba <vfs_unlink+aa/1a0>
> 6: 0f 8e 58 16 00 00 jle 1664 <_EIP+0x1664>
> Code; c013eec0 <vfs_unlink+b0/1a0>
> c: 85 db test %ebx,%ebx
> Code; c013eec2 <vfs_unlink+b2/1a0>
> e: 74 16 je 26 <_EIP+0x26>
> Code; c013eec4 <vfs_unlink+b4/1a0>
> 10: 89 d8 mov %ebx,%eax
> Code; c013eec6 <vfs_unlink+b6/1a0>
> 12: 8b 5c 00 00 mov 0x0(%eax,%eax,1),%ebx
>
>
> Sorry for bad news. As before, the 'rm file' succeeded, prior to the
> segfault. I put the dmesg (before oops) and 'grep = .config' up on
> <http://bugsplatter.mine.nu/test/linux-2.4/sempro/> with -rc1a suffix
>
> Repeat with extract 2.4.32 + patches --> same, note that the oops is
> only on deleting file over NFS, I noticed 2.6.16.20 has extra NFS
> stuff around this area.

Thanks for the info and the tests, maybe Al will have some insight here ?

> grant@sempro:~$ dmesg >dmesg
> grant@sempro:~$ rm dmesg
> grant@sempro:~$ dmesg >/home/share/dmesg-test
> grant@sempro:~$ rm /home/share/dmesg-test
> Segmentation fault
>
> Grant.

Cheers,
Willy