From: OGAWA Hirofumi I got the oops after some hotplug events. And the similar oops can reproduce by the following step. plug usb-storage (e.g. scsi_host of usb is "host5", and device is sde) # mount /dev/sde1 /mnt # echo 1 > /sys/block/sde/device/delete # echo - - - > /sys/class/scsi_host/host5/scan # echo - - - > /sys/class/scsi_host/host5/scan # echo - - - > /sys/class/scsi_host/host5/scan unplug usb-storage # umount /mnt general protection fault: 0000 [1] SMP CPU 1 Modules linked in: nls_iso8859_1 nls_cp437 vfat fat nls_base nfsd exportfs p4_clockmod speedstep_lib cpufreq_ondemand freq_table thermal fan button processor ac battery autofs4 ipv6 nfs lockd nfs_acl sunrpc deflate zlib_deflate zlib_inflate twofish twofish_common serpent blowfish des cbc ecb blkcipher aes xcbc sha256 sha1 crypto_null hmac crypto_hash cryptomgr af_key binfmt_misc dm_snapshot dm_mirror dm_mod eth1394 usb_storage snd_hda_intel snd_hda_codec snd_pcm_oss snd_mixer_oss snd_pcm snd_timer r8169 snd i2c_i801 bitrev crc32 ehci_hcd uhci_hcd intel_agp ohci1394 ieee1394 rng_core usbcore soundcore snd_page_alloc i2c_core parport_pc parport evdev sg sr_mod cdrom floppy Pid: 3780, comm: umount Not tainted 2.6.20-rc4 #1 RIP: 0010:[] [] sysfs_remove_file+0x8/0x12 RSP: 0018:ffff810059703b58 EFLAGS: 00010286 RAX: ffff8100596bba50 RBX: ffff8100596bba50 RCX: ffff810059703b68 RDX: ffff810059703b48 RSI: 6b6b6b6b6b6b6b6b RDI: 6b6b6b6b6b6b6b6b RBP: ffff810059703b58 R08: ffff8100596bbac8 R09: 0000000000000000 R10: ffff8100596bba28 R11: 0000000000000400 R12: 6b6b6b6b6b6b6b6b R13: ffff81005e303650 R14: ffff81005e9cf1b8 R15: ffff8100596bba50 FS: 00002af1e22111d0(0000) GS:ffff81005f7a9898(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007fff3c0145e8 CR3: 0000000059600000 CR4: 00000000000006e0 Process umount (pid: 3780, threadinfo ffff810059702000, task ffff81005f3997f0) Stack: ffff810059703b78 ffffffff8023a07a ffff8100596bba50 ffff8100596bba50 ffff810059703ba8 ffffffff8023a110 ffff81005e303478 ffff8100596bba50 ffff8100596bba28 ffff81005e303478 ffff810059703bd8 ffffffff80249049 Call Trace: [] device_remove_file+0x26/0x33 [] device_del+0x3a/0x1d1 [] scsi_target_reap_usercontext+0x54/0xbb [] execute_in_process_context+0x27/0x56 [] scsi_target_reap+0x98/0xac [] scsi_device_dev_release_usercontext+0xab/0xd8 [] execute_in_process_context+0x27/0x56 [] scsi_device_dev_release+0x17/0x19 [] device_release+0x31/0x70 [] kobject_cleanup+0x53/0x77 [] kobject_release+0x0/0xf [] kobject_release+0xd/0xf [] kref_put+0x63/0x6d [] kobject_put+0x19/0x1b [] put_device+0x15/0x17 [] scsi_device_put+0x3d/0x42 [] scsi_disk_put+0x2e/0x3f [] sd_release+0x7b/0x82 [] __blkdev_put+0x7c/0x15e [] __blkdev_put+0x12b/0x15e [] blkdev_put+0xb/0xd [] close_bdev_excl+0x19/0x1e [] kill_block_super+0x36/0x3b [] deactivate_super+0x6f/0x84 [] mntput_no_expire+0x56/0x87 [] path_release_on_umount+0x1d/0x21 [] sys_umount+0x21f/0x254 [] sys_newstat+0x22/0x3c [] system_call+0x7e/0x83 By "echo 1 > /sys/block/sde/device/delete", sdev->sdev_state became SDEV_DEL. The problem is in, scsi_probe_and_add_lun() -> scsi_device_lookup_by_target() -> __scsi_device_lookup_by_target() by "echo - - - > /sys/class/scsi_host/host5/scan". The first scan is still not problem. Since founded existence device is already SDEV_DEL, it just adds a new device. The problem is second re-scan, it is looking a existence device up. In this case it is SDEV_DEL device, not newly added device by first scan. This patch fixes the oops by excluding the SDEV_DEL devices in __scsi_device_lookup_by_target(). Signed-off-by: OGAWA Hirofumi Cc: James Smart On Wed, 10 Jan 2007 08:31:54 -0500 James Smart wrote: > I don't believe this is a valid fix. This is yet another case > of the reuse-after-free issues on sdevs. The real issue is the > deleted sdev isn't truly getting deleted due to references, and > we're deadlocked trying to allocate a new one while the old one > is outstanding. This fix just jumps over things. You're actually > using a partially torn down sdev that, if the refcounts ever > decremented, would be zapped - and you would be in a bunch of trouble. Signed-off-by: Andrew Morton --- drivers/scsi/scsi.c | 2 ++ 1 file changed, 2 insertions(+) diff -puN drivers/scsi/scsi.c~fix-the-reproducible-oops-in-scsi drivers/scsi/scsi.c --- a/drivers/scsi/scsi.c~fix-the-reproducible-oops-in-scsi +++ a/drivers/scsi/scsi.c @@ -938,6 +938,8 @@ struct scsi_device *__scsi_device_lookup struct scsi_device *sdev; list_for_each_entry(sdev, &starget->devices, same_target_siblings) { + if (sdev->sdev_state == SDEV_DEL) + continue; if (sdev->lun ==lun) return sdev; } _