Re: Linux 2.4.33-rc1

[Grant Coady <gcoady.lk@gmail.com>]

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);
> 	}
> 	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.

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.
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