Hello I am facing one problem with unionfs. The bug description is given below. Most often i found unionfs throws kernel NULL pointer dereference error. Till now i am not sure what is this problem all about. I have used below packages but still i can't find any luck. Any clue will be helpfull. linux-ubuntu-modules-2.6.24-24-xen linux-ubuntu-modules-2.6.24-22-xen linux-ubuntu-modules-2.6.24-19-xen [ 50.865463] Unable to handle kernel NULL pointer dereference at 0000000000000010 RIP: [ 50.865476] [<ffffffff88007246>] :unionfs:newputmap+0xf6/0x1b0 [ 50.865489] PGD 186d3067 PUD 18f49067 PMD 0 [ 50.865494] Oops: 0002 [1] SMP [ 50.865497] CPU 0 [ 50.865499] Modules linked in: af_packet ipt_REJECT xt_tcpudp nf_conntrack_ipv4 xt_state nf_conntrack iptable_filter ip_tables x_tables evdev ext3 jbd mbcache unionfs [ 50.865512] Pid: 3940, comm: unionctl Not tainted 2.6.24-24-xen #1 [ 50.865515] RIP: e030:[<ffffffff88007246>] [<ffffffff88007246>] :unionfs:newputmap+0xf6/0x1b0 [ 50.865521] RSP: e02b:ffff88001851fbb8 EFLAGS: 00010246 [ 50.865523] RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000002 [ 50.865526] RDX: 0000000000000010 RSI: 0000000000000002 RDI: 0000000000000000 [ 50.865528] RBP: ffff880019685200 R08: ffff8800197260f0 R09: 0000000000000002 [ 50.865530] R10: 0000000000000001 R11: ffffffff8031e6a0 R12: ffff88001951fd00 [ 50.865533] R13: ffff880019726000 R14: 0000000000000010 R15: 0000000000000000 [ 50.865537] FS: 00007fc0c2fc56e0(0000) GS:ffffffff805c7000(0000) knlGS:0000000000000000 [ 50.865539] CS: e033 DS: 0000 ES: 0000 [ 50.865541] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 50.865543] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000000 [ 50.865546] Process unionctl (pid: 3940, threadinfo ffff88001851e000, task ffff8800177b5040) [ 50.865549] Stack: ffff880018ad34e0 ffff880019726000 0000000000000000 00000000ffffffea [ 50.865554] 0000000000000000 ffffffff8800781f 0000000000000000 ffff880017a05000 [ 50.865558] 0000000000000020 ffffffff802bf184 0000000000000000 0000000000000001 [ 50.865562] Call Trace: [ 50.865568] [<ffffffff8800781f>] :unionfs:unionfs_ioctl_delbranch+0xcf/0x410 [ 50.865575] [<ffffffff802bf184>] sync_inodes_sb+0x94/0xb0 [ 50.865579] [<ffffffff8029f975>] do_remount_sb+0xd5/0x150 [ 50.865583] [<ffffffff802b777c>] do_mount+0x4ac/0x810 [ 50.865587] [<ffffffff80272e0d>] find_lock_page+0x3d/0x110 [ 50.865590] [<ffffffff802752e3>] filemap_fault+0x1d3/0x3e0 [ 50.865595] [<ffffffff8033a211>] __up_read+0x21/0xb0 [ 50.865600] [<ffffffff8024a6ed>] search_exception_tables+0x1d/0x30 [ 50.865604] [<ffffffff80473ddb>] do_page_fault+0x3eb/0x11e0 [ 50.865608] [<ffffffff80287741>] handle_mm_fault+0x1d1/0xd60 [ 50.865611] [<ffffffff802a912a>] do_path_lookup+0x8a/0x250 [ 50.865614] [<ffffffff80278540>] get_page_from_freelist+0xc0/0x520 [ 50.865618] [<ffffffff80278acd>] __alloc_pages+0x9d/0x3c0 [ 50.865622] [<ffffffff80278e77>] __get_free_pages+0x87/0xa0 [ 50.865625] [<ffffffff802b822b>] sys_mount+0x9b/0x100 [ 50.865629] [<ffffffff8020c698>] system_call+0x68/0x6d [ 50.865631] [<ffffffff8020c630>] system_call+0x0/0x6d [ 50.865634] [ 50.865635] [ 50.865635] Code: 4c 89 24 c2 31 c0 5b 5d 41 5c 41 5d 41 5e c3 48 8b 45 38 48 [ 50.865645] RIP [<ffffffff88007246>] :unionfs:newputmap+0xf6/0x1b0 [ 50.865651] RSP <ffff88001851fbb8> [ 50.865653] CR2: 0000000000000010 [ 50.865660] ---[ end trace d89be748ddf857e4 ]--- [ 50.865663] WARNING: at /build/buildd/linux-2.6.24/debian/build/custom-source-xen/kernel/exit.c:917 do_exit() [ 50.865667] Pid: 3940, comm: unionctl Tainted: G D 2.6.24-24-xen #1 [ 50.865669] [ 50.865669] Call Trace: [ 50.865672] [<ffffffff8023971e>] do_exit+0x7de/0x9a0 [ 50.865676] [<ffffffff804743b6>] do_page_fault+0x9c6/0x11e0 [ 50.865680] [<ffffffff802e0fe3>] task_dumpable+0x23/0x40 [ 50.865685] [<ffffffff802b1b9b>] dput+0xab/0x140 [ 50.865687] [<ffffffff802a5eb9>] __follow_mount+0x29/0xa0 [ 50.865690] [<ffffffff802a610f>] do_lookup+0x8f/0x250 [ 50.865693] [<ffffffff80472287>] error_exit+0x0/0x79 [ 50.865697] [<ffffffff8031e6a0>] apparmor_capable+0x0/0x50 [ 50.865702] [<ffffffff88007246>] :unionfs:newputmap+0xf6/0x1b0 [ 50.865707] [<ffffffff880072cb>] :unionfs:newputmap+0x17b/0x1b0 [ 50.865713] [<ffffffff8800781f>] :unionfs:unionfs_ioctl_delbranch+0xcf/0x410 [ 50.865716] [<ffffffff802bf184>] sync_inodes_sb+0x94/0xb0 [ 50.865720] [<ffffffff8029f975>] do_remount_sb+0xd5/0x150 [ 50.865723] [<ffffffff802b777c>] do_mount+0x4ac/0x810 [ 50.865726] [<ffffffff80272e0d>] find_lock_page+0x3d/0x110 [ 50.865728] [<ffffffff802752e3>] filemap_fault+0x1d3/0x3e0 [ 50.865732] [<ffffffff8033a211>] __up_read+0x21/0xb0 [ 50.865735] [<ffffffff8024a6ed>] search_exception_tables+0x1d/0x30 [ 50.865738] [<ffffffff80473ddb>] do_page_fault+0x3eb/0x11e0 [ 50.865741] [<ffffffff80287741>] handle_mm_fault+0x1d1/0xd60 [ 50.865743] [<ffffffff802a912a>] do_path_lookup+0x8a/0x250 [ 50.865746] [<ffffffff80278540>] get_page_from_freelist+0xc0/0x520 [ 50.865750] [<ffffffff80278acd>] __alloc_pages+0x9d/0x3c0 [ 50.865753] [<ffffffff80278e77>] __get_free_pages+0x87/0xa0 [ 50.865756] [<ffffffff802b822b>] sys_mount+0x9b/0x100 [ 50.865759] [<ffffffff8020c698>] system_call+0x68/0x6d [ 50.865761] [<ffffffff8020c630>] system_call+0x0/0x6d [ 50.865763] Killed -- Regards Arun Sharma