Bug 6641

Summary: BUG: unable to handle kernel paging request at virtual address feededed
Product: File System Reporter: Tomasz Torcz (zdzichu)
Component: ReiserFSAssignee: ReiseFS developers team (reiserfs-devel)
Status: REJECTED UNREPRODUCIBLE    
Severity: normal    
Priority: P2    
Hardware: i386   
OS: Linux   
Kernel Version: v2.6.17-rc5 Subsystem:
Regression: --- Bisected commit-id:

Description Tomasz Torcz 2006-06-04 09:54:36 UTC
Most recent kernel where this bug did not occur: v2.6.17-rc5 (it happend only once)

Distribution: Slackware -current

Hardware Environment: Sempron CPU on NForce2 MB. Seagate SATA disk driven by
sata_sil. 

Software Environment: LVM2 with few volumes, one of them (my ~) on dm-crypt, but
rootfs is not crypted. All filesystems are reiserfs mounted with  "user_xattr,acl". 

Problem Description:

during updatedb run I got:

BUG: unable to handle kernel paging request at virtual address feededed
 printing eip:
c0160fb1
*pde = 00000000
Oops: 0000 [#1]
Modules linked in: mga drm ipv6 sha256 dm_crypt binfmt_misc uhci_hcd i2c_nforce2
+eth1394 ohci_hcd ehci_hcd forcedeth snd_intel8x0 snd_ac97_codec snd_ac97_bus
+sata_nv ohci1394 ieee1394 tuner tvaudio bttv video_buf firmware_class ir_common
+btcx_risc tveeprom e1000 udf usb_storage usbcore cpufreq_nforce2 lp parport
+w83627hf hwmon_vid i2c_isa
CPU:    0
EIP:    0060:[<c0160fb1>]    Not tainted VLI
EFLAGS: 00010206   (2.6.17-rc5 #63)
EIP is at __d_find_alias+0x1c/0xa2
eax: 00008000   ebx: feededed   ecx: feededed   edx: cfe98954
esi: cde98918   edi: cde98918   ebp: cfe9893c   esp: c4d27d10
ds: 007b   es: 007b   ss: 0068
Process updatedb (pid: 18083, threadinfo=c4d27000 task=d92b7570)
Stack: 00000001 cfe9893c dc3ed190 00000000 d509e42c c0161825 00000001 c4d27d3c
       cfe9893c c0180050 dc3ed190 00000001 00000000 00000000 00000000 00000000
       00000000 df4d39f4 00000000 df4d39c4 00000070 c66b8154 00000003 c599e784
Call Trace:
 <c0161825> d_splice_alias+0x17/0x86  <c0180050> reiserfs_lookup+0xe2/0xf1
 <c01597a3> real_lookup+0x53/0xad  <c01599c0> do_lookup+0x49/0x78
 <c015a00c> __link_path_walk+0x61d/0x9d6  <c0191d9b> pathrelse+0x1b/0x26
 <c0188909> reiserfs_readdir+0x3db/0x3ea  <c015a406> link_path_walk+0x41/0xaa
 <c01de7cc> strncpy_from_user+0x2d/0x4c  <c015a770> do_path_lookup+0x199/0x1e4
 <c015a9cb> __user_walk_fd+0x29/0x3a  <c0156448> vfs_lstat_fd+0x12/0x39
 <c01569d4> sys_lstat64+0xf/0x23  <c0102933> syscall_call+0x7/0xb
Code: 89 50 04 89 02 89 5b 04 89 59 24 5b 89 c8 c3 55 89 c5 57 56 31 f6 53 51 89
+14 24 8b 48 18 8d 50 18 39 d1 0f 84 80 00 00 00 89 cb <8b> 09 0f 18 01 90 0f b7
+45 28 8d 7b c4 25 00 f0 00 00 3d 00 40
EIP: [<c0160fb1>] __d_find_alias+0x1c/0xa2 SS:ESP 0068:c4d27d10
 BUG: updatedb/18083, lock held at task exit time!
 [d509e49c] {inode_init_once}
.. held by:          updatedb:18083 [d92b7570, 118]
... acquired at:               real_lookup+0x1c/0xad

<a href="http://lkml.org/lkml/2006/5/29/51">Original report</a>
Comment 1 Tomasz Torcz 2006-06-04 09:56:09 UTC
Analysis by Chuck Ebbert:

#v+
Oops happened here:

static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
{
        struct list_head *head, *next, *tmp;
        struct dentry *alias, *discon_alias=NULL;

        head = &inode->i_dentry;
        next = inode->i_dentry.next;
        while (next != head) {
                tmp = next;
====>           next = tmp->next;
                prefetch(next);


tmp contained 0xfeededed, which was an invalid kernel address.

So while walking the dentry list for the inode, an invalid next pointer was
found, and it wasn't the very first one, i.e. it wasn't from the head
(if it were, then eax and ebp would be identical.)

want_discon (arg 2) was 1

[...]

   f:   55                        push   %ebp
  10:   89 c5                     mov    %eax,%ebp
  12:   57                        push   %edi
  13:   56                        push   %esi
  14:   31 f6                     xor    %esi,%esi
  16:   53                        push   %ebx
  17:   51                        push   %ecx
  18:   89 14 24                  mov    %edx,(%esp)
  1b:   8b 48 18                  mov    0x18(%eax),%ecx
  1e:   8d 50 18                  lea    0x18(%eax),%edx
  21:   39 d1                     cmp    %edx,%ecx
  23:   0f 84 80 00 00 00         je     a9 <_EIP+0xa9>
  29:   89 cb                     mov    %ecx,%ebx
00000000 <_EIP>:
   0:   8b 09                     mov    (%ecx),%ecx   <=====
   2:   0f 18 01                  prefetchnta (%ecx)
   5:   90                        nop
   6:   0f b7 45 28               movzwl 0x28(%ebp),%eax
   a:   8d 7b c4                  lea    0xffffffc4(%ebx),%edi
   d:   25 00 f0 00 00            and    $0xf000,%eax


#v-