Re: Linux 2.4.33-rc1

Marcelo Tosatti
2006-06-18T13:36:31Z

On Sat, Jun 17, 2006 at 08:21:44AM +1000, Grant Coady wrote:
> On Fri, 16 Jun 2006 15:14:19 -0300, Marcelo Tosatti <marcelo@kvack.org> wrote:
>
> >Here is 2.4.33-rc1.
>
> I provoked a network related oops as user 'grant', with this CLI input
> boo-boo on an ssh terminal:
>
> grant@sempro:~$ rm /home/share/config-2.6.17-rc6-mm1a dmesg-2.6.17-rc6-mm1a
>
> /home/share is an NFS mounted directory
>
> Was able to login direct as root and copy the oops info with mouse (gpm)
> copy/paste, but console locked up on localnet access, here's the guff:
>
> ksymoops 2.4.11 on i686 2.4.33-rc1. Options used
> -v /home/grant/linux/linux-2.4.33-rc1/vmlinux (specified)
> -k /proc/ksyms (default)
> -l /proc/modules (default)
> -o /lib/modules/2.4.33-rc1/ (default)
> -m /boot/System.map-2.4.33-rc1 (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: f6e2fd08 edi: f5839ac0 ebp: f6e2fc80 esp: f5889f6c
> ds: 0018 es: 0018 ss: 0018
> Process rm (pid: 243, stackpage=f5889000)
> Stack: f6e2fc80 f5839ac0 f5839ac0 f7bdd000 f5889f90 f5839ac0 c013f066 f6e2fc80
> f5839ac0 f6e36440 c19ac440 f7bdd00c 00000016 be8f2661 00000010 00000000
> 00000004 f5888000 bffff96b 08051050 bffff758 c0106eff bffff96b 00000002
> Call Trace: [<c013f066>] [<c0106eff>]
> Code: ff 80 88 00 00 00 0f 8e 2e 16 00 00 85 db 74 16 89 d8 8b 5c
>
>
> >>EIP; c013eeb4 <vfs_unlink+a4/1a0> <=====
>
> >>esi; f6e2fd08 <_end+36a9405c/386be3d4>
> >>edi; f5839ac0 <_end+3549de14/386be3d4>
> >>ebp; f6e2fc80 <_end+36a93fd4/386be3d4>
> >>esp; f5889f6c <_end+354ee2c0/386be3d4>
>
> Trace; c013f066 <sys_unlink+b6/120>
> 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 2e 16 00 00 jle 163a <_EIP+0x163a>
> 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

Grant,

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);